LIBRARY OF CONGRESS. 



Chap. Copyright No. 

.HI 

UNITED STATES OF AMERICA. 



Anomalies of Refraction 



AND OF THE 



Muscles of the Eye 



BY 
/ 

FLAVEL B. TIFFANY, A.M., M.D , 

Professor of Ophthalmology and Otology of the University Medical 

College of Kansas City, Mo.; Oculist and Aurist to the 

University Hospital; Oculist to the 

M. K. & T. R. R. 

Member of the International Medical Congress, Pan-American Association, 
American Medical Association, American Microscopical Society, 
Missouri State Medical Association, Kansas State Med- 
ical Association, Missouri Valley 
Medical Society, 
Etc. 



Vox a occasu solis. 



AUTHOR'S FOURTH EDITION 



KANSAS CITY, MO. : 
HUDSON-KIMBRRI v Y PUBLISHING CO. 

1900. 



74510 



Library of Congress 

Two Copies Received 
NOV 12 1900 

a Copyright entry 

SECOND COPY 
Delivered to 

ORDER DIVISION 

DEC 18 1900 




<^< 



*v 



Entered according to Act of Congress in the year 1894, 

By HUDSON-KIMBERIvY PUBLISHING CO„ 

In the Office of the Librarian of Congress, at Washington, D C. 



Entered according to Act of Congress in the year 1900, 

By HUDSON-KIMBERLY PUBLISHING CO., 

In the Office of the Librarian of Congress at Washington, D. C. 



Electrotyped and Printed 

By H -K. PUB. CO., 
1014 16 Wyandotte St., K.C. 



List of Plates. 



Plate. Page- 

I. Professor Von Helmholtz 11 

II. Professor Donders 13 

III. Professor Edmund Landolt 17 

TV. Ciliary Region 73 

V. Catoptric Test (Donders) —colored 77 

VI. Fundus— colored 107 

VII. Circles of Diffusion in Chromatic Test (Iyandolt) — colored. . .126 

V III. Test with Chromoscope — colored 195 

IX. Skiascopy 197 

X. Convergent Strabismus 266 

XI. Convergent Strabismus Corrected 267 

XII. Convergent Strabismus Previous and Subsequent to the 

Operation 268 



List ok Illustrations. 



T 

Pig. Page. 

1 Ray, beam, and pencil of light 21 

2 Rays from candle flame emanating in all directions 21 

3 Image through small aperture 22 

4 Reflection of light from plane surface — angles of incidence 

and of reflection. . . 23 

5 Reflection of light from plane mirror 23 

6 Reflection from mirror when horizontal 24 

7 Reflection from surface of water 24 

8 Vertex, principal axis, and center of curvature in curved 

mirrors 25 

9 Reflection from concave mirrors 25 



IV UST OF ILLUSTRATIONS. 

Fig-. Page. 

10 Principal focus of concave mirror 27 

11 Reflection by concave mirror of rays coming from between 

principal focus and the mirror 27 

12 Reflection from convex mirrors — principal virtual focus 28 " 

13 Virtual focus from divergent rays 28 

14 Image from concave mirror when object is beyond center of 

curvature 29 

15 Image from concave mirror when object is between mirror and 

principal focus 30 

16 Image of one looking into a concave mirror when near it 30 

17 Reflection of rays when object is at the principal focus 31 

18 Image produced by convex mirrors 31 

] 9 Refraction of rays 34 

20 Cause of refraction 34 

21 Effect of refraction 35 

22 Section of prism 36 

23 Deflection of image through prism 37 

Spherical lenses 37 

24 Refraction by double convex lens — principal focus 38 

25 Focal length of plano-convex and of double convex lenses. ... 39 

26 Principal axis of convex lens 39 

27 Optical center and secondary axis of convex lens 40 

28 Refraction by convex lens of rays emanating from the princi- 

pal focus 40 

29 Refraction by convex lens of rays coming from beyond the 

principal focus at a finite distance 41 

30 Refraction by convex lens of rays coming from between the 

lens and the principal focus 41 

31 Refraction of parallel rays by double concave lens 41 

32 Principal virtual focus of double concave lens 42 

33 Image produced by convex lens when object is at a distance 

greater than twice the focal length of the lens 43 

34 Image when object is less than twice the focal length from lens 44 

35 Image formed by convex lens when object is at a distance 

equal to twice the focal length of the lens 44 

36 Object at the principal focus . 45 

37 Image produced by convex lens when object is between the 

lens and the principal focus 45 

38 Simple microscope 46- 

39 Use of convex lens for discharging cannon (burning glass) .... 46 

40 Diagram of compound microscope , 47 

41 Diagram of astronomical telescope 47 

42 Diagram of camera obscura 48 

43 Formation of images by double concave lenses 48 

44 Aperture of lens 49 

45 Spherical aberration 49 



LIST OF ILLUSTRATIONS. V 

Fig. Page. 

46 Spherical aberration 49 

47 Solar spectrum 50 

48 Recomposition of light by two prisms 50 

49 Recomposition of light by prism and concave mirror 51 

50 Chromatic aberration 51 

51 Achromatic lens 52 

52 Section of eye . r 3 

53 Retina 56 

54 Yellow spot 57 

55 Experiment, showing the blind spot 58 

56 Optic axis and visual line 60 

57 Visual angle 61 

18 Visual angle - 62 

59 Optic angle 63 

60 Emmetropic eye 64 

61 Myopic eye 65 

62 Hyperopic eye 66 

63 Accommodation of the eye 66 

64 Angle alpha and angle gamma 67 

65 Astigmatism 68 

66 Accommodation of the eye 72 

67 Catoptric test 76 

68 Ciliary region in hyperopic eye 78 

69 Ciliary region in emmetropic eye 78 

70 Ciliary region in myopic eye , 79 

71 Experiments of Hensen and Voelckers ' 82 

72 Trial case (Meyrowitz) 85 

73 Stenopaic, ground glass, and opaque discs, etc 86 

74 Trial frames 86 

75 Snellen's type 87 

75 Maddox double prism and rod, chromatic glass, and half-ground 

glass 88 

76 Dial (test for astigmatism) 90 

77 Stenopaic disc with slot 91 

78 Pupilometer 92 

79 Keratoscope 93 

80 Prisoptometer , 94 

81 Discs in prisoptometry. ....... 95 

82 Tests by the prisoptometer. .«.,.... 95 

83 Oblique method 96 

84 Loring's ophthalmoscope . 97 

85 L/Oring's ophthalmoscope 98 

86 Iviebreich's ophthalmoscope 99 

87 Dr. Fox'sl ophthalmoscope 100 

88 Direct method: 102 

89 Direct method 104 



VI LIST OF ILLUSTRATIONS. 

Fig. Page. 

90 Direct method 105 

91 Indirect method 109 

92 Indirect method 110 

93 Optic disc 112 

94 Hyaloid artery 113 

Tablet for recording magnified image of the fundus of the eye.. 116 

95 Skiascopy (shadow test) 119 

96 Retinoscopy (Nettleship) 121 

97 Fournet's refractometer for retinoscopy 122 

98 Fournet's refractometer in use 123 

99 Bull's optometer 125 

100 Chromatic glass (L-andolt) 126 

101 Schemer's test 128 

102 Perimeter 130 

103 Myopic eye 132 

101 Pupilometer 150 

105 Hyperopic eye 155 

106 Trial box (Geneva Optical Co.) 165 

107 Astigmatism 179 

108 Circles of diffusion in astigmatism 179 

109 Fundus in astigmatism. 183 

110 Dial (test for astigmatism i 184 

111 Javal and Schioetz ophthalmometre (astigmometer) 185 

112 Telescope of ophthalmometre 186 

113 Curved horizontal bar of ophthalmometre 187 

114 Plaques of ophthalmometre 188 

115 J. and S. ophthalmometre in use 188 

116 Overlapping of the mires 189 

117 Separation of the mires 190 

121 Chromoscope 194 

122 Chromatic glass 195 

123 Bar frame 205 

124 Pinch-nose 205 

125 Centering of glasses as to the pupils 205 

126 Cylinder 209 

127 Refraction of a cylinder 207 

128 Various forms of cylinders 207 

129 Tore 2C8 

130 Extrinsic ocular muscles 221 

131 Model representing the muscles 222 

132 Extrinsic ocular muscles 223 

133 Homonymous diplopia produced by prism 228 

134 Heteronymous diplopia produced by prism. . 228 

135 Homonymous diplopia from esophoria .230 



LIST OF ILLUSTRATIONS. VII 

Fig:. Page. 

136 Heteronymous diplopia from exophoria 230 

137 Line and dot test 236 

138 Line and dot test for insufficiency of abductors and adductors. .236 

139 Maddox's rod 238 

140 Test with Maddox's rod for insufficiency of superior and in- 

ferior recti 238 

141 Test with Maddox's rod for insufficiency of abductors and 

adductors 239 

142 Double prism (Maddox) 240 

143 Test for heterophoria 240 

144 Von Graefe's line and dot test 241 

145 Esophoria and exophoria 241 

146 Hyperphoria and cataphoria 241 

147 Hyper-esophoria and hyper-exophoria 242 

148 Eso-cataphoria and exo-cataphoria 242 

149 Letter test for heterophoria 242 

150 Letter test in use 243 

151 Stevens's phorometer £44 

152 Test with phorometer 245 

Prince's phorometer 246 

153 Line test for insufficiency ot oblique muscles 250 

154 Strabismometer 253 

155 Perimeter 254 

156 Divergent strabismus 261 

157 Divergent strabismus (corrected) 261 

158 Convergent strabismus. . . 264 

159 Convergent strabismus (corrected) 265 

160 Convergent strabismus 268 

161 Glass having its focus in the center 269 

1 62 Glass having its focus excentric 269 

163 Glasses correctly centered , 270 

164 Glasses correctly centered 270 

165 Glasses tilted 270 

166 Glasses tilted 270 

167 Glasses decentered 271 

168 Glasses decentered inward 271 

169 Glasses decentered outward 271 

170 Hooked bows 272 

171 Straight bows 273 

172 Pinch-nose 273 

173 Bar frame 274 

174 Aluminum protectors 275 

175 Goggles 275 

176 Shade 275 

177 Split glasses 276 

178 Cement bifocal lens 276 

179 Solid bifocal lens 276 



TABLE OF CONTENTS. 

CHAPTER VI. 
How to Examine the Eye. 
Test with trial lenses from trial box— Snellen's test type— Test 
with keratoscope— Examination by the prisoptometer — Ex- 
amination by the ophthalmoscope — Direct method — Indi- 
rect method— Oblique method — Enlargement of ophthalmo- 
scopic images and how to determine the amount — Skiascopy 
— Chromatic test — Scheiner's test — Optometry by the peri- 
meter 84-131 

CHAPTER VII. 
Myopia. 
Definition — Causes — Symptoms — Pathology — Diagnosis — Prog- 
nosis—Sequelae — Case- -Prophylactic treatment — Treatment 
by glasses — Luxation for myopia 132-154 

CHAPTER VIII. 
Hypermetropia. 
Definition — Symptoms — Cause — Diagnosis — Prognosis — Se- 
quelae—Treatment — Case 155-176 

CHAPTER IX. 
Astigmatism. 
Definition — History — Forms — Cause — Symptoms — Diagnosis- 
Test with prisoptometer — Test by keratoscope — Test by the 
chromoscope — Test by ophthalmoscope — Skiascopy — Test 
by trial glasses from trial box — Prognosis — Treatment — 
Hypothetical cases — Cylindrical glasses — Torical glasses — 
Hyperbolical glasses 177-209 

CHAPTER X. 

Anisometropia, Aphakia, and Presbyopia. 

Anisometropia — Treatment — Aphakia— Presbyopia 210-219 

CHAPTER XI. 
Heterophoria. 
Heterophoria — Orthophoria — Esophoria — Exophoria— Hyper- 
phoria — Cataphoria — Hyper-esophoria — Hyper-exophoria — 
Eso-cataphoria — Exo-cataphoria — Extrinsic muscles of the 
eye — Horopter — Homonymous diplopia — Heteronymous di- 
plopia — How to test the strength of the muscles and detect 
any existing insufficiency thereof— Vertical line test-Mad- 
dox rod test — Von Graefe line and dot test — Phorometer — 
Treatment — Rhythmic exercise with prisms — How to de- 
tect and correct insufficiency of the oblique muscles, accord- 
ing to Savage— Treatment ., 220-251 



TABLE OF CONTENTS. 

CHAPTER XII. 
Strabismus. 
Definition — Kinds — Strabismometer — Perimeter — Angle of de- 
viation — Cause — Time of appearance of strabismus — Treat- 
ment — Tenotomy — Advancement operation 252-268 

CHAPTER XIII. 

Spectacles. 
Glasses cen'ered and decentered - Glasses poised properly and 
tilted — Hook bows — Ordinary frames — Nose glass — Bar 
frame — Protecting glass — Aluminum protector— Goggles — 
Shades — Bifocal lenses— Dioptric — Dioptre — Table of diop- 
tres compared with inches 269-279 



Appendix. 



PART I. 
Synopsis of data gathered from the examination of 2,040 school- 
children of the public schools of Kansas City, Universities 
of Kansas and Missouri, State Normal and other district 
schools (taken from a paper read before the Ninth Interna-, 
tional Medical Congress at Washington, D. C, 1887) 280-284 

PART II. 
Cabinet for test types — Prism-measarmg and lens-centering 

instrument — Lens-measurer 285-289 

Test types 290-294 



preface: to first edition. 

In no branch of medicine or surgery withm the last 
decade has there been more attention given or more dis- 
coveries or advancements made than in the department of 
ophthalmology; particularly, the anomalies and affections 
of the ocular muscles and of refraction; and yet, these 
vast subjects of heterophoria and ametropia are still wrapped 
in a halo of uncertainties. That some anomaly of the ocu- 
lar muscles, of refraction, or of both, is accountable for 
many of the pains, aches, and ills of the body and for many 
of the different forms of chorea and hysteria, is being more 
and more recognized by the profession in general. 

In no branch of medicine have there been invented so 
many instruments and apparati for the disclosure of disease as 
for those anomalies and affections which are incident to this 
little organ of vision ; and in no branch of the science, 
it would seem, is it so necessary that a settled and definite 
plan be adhered to in the ferreting out of these occult affec- 
tions and complications as in ophthalmology. The gen- 
eral practitioner is often unable to cure cases of these anom- 
alies, and sends them to the oculist, and the oculist is 
frequently put to his wits end and ofttimes completely 
"stumped" in trying to disclose the real pathological or 
functional disorder or defect. 

It is said that the inmates of insane asylums, homes for 
the feebleminded, and prisons are, with few exceptions, 
either ametropic or heterophoric. It would seem, then, that 
these anomalies may bear some intimate relation to mans 
moral nature. The manner and degree in which a ray of 



8 PREFACE. 

light is bent from its course as it passes through the differ- 
ent dioptric media, together with the beautiful and complete 
mechanism of accommodation which enables the eye to re- 
ceive these impressions, whether they come from near or 
afar, has much to do with man's correct estimate of the 
material world about him. 

That the faculty of vision shapes largely the destiny of 
man, warps or fashions his fate or his moral nature, there 
is little doubt. 

The subject of " eye-sight 1 ' of school children is now 
attracting the attention not only of the medical profession, 
but of thinking people throughout the land, and especially 
of educators. Our venerated teacher, Prof. Donders, taught 
us that the ideal eye, the normal eye, as to its refraction, is 
so constructed and adjusted as to bring parallel rays of light 
to a focus upon its retina without any effort of accommo- 
dation; in other words, it is the emmetropic eye. 

In some recent publications it has been asserted that 
the hyperopic eye is the normal condition, and that this 
normal eye is always keyed up to a certain amount of mus- 
cular tension, whether it is adjusted for near or for distant 
objects, and one writer says that the whole subject of refrac- 
tion and accommodation, in his opinion, should be rewritten. 
Be this as it may, the subject under consideration is still in 
a mist, and I may be pardoned if I, in my humble way, con- 
tribute my mite in the endeavor to shed more light on the 
subject, from my personal experience and observation, both 
in my public clinic and private practice. 

In writing this little volume, it has been my purpose to 
present the subject in as clear, brief, and concise a manner as 
possible, embracing all essentials, besides collaborating recent 
advancements not to be found in the existing books. I have 
also been stimulated to write the book from repeated requests 
made by my students to whom I have presented this subject 
didactically and clinically for the past thirteen years. To 
one of these students in particular am I indebted for the 
valuable assistance he has rendered by his knowledge of 
Stenography, by the making of many of the drawings, assist- 



PREFACE. 9 

ing in the proof-reading, etc. It is to my friend and former 
student, H. D. Jerowitz, M.D., I say, that I am indebted for 
valuable assistance. 

To another, who by her keen, bright intellect and accu- 
rate, honest mind has rendered me much assistance in this 
as in other of my literary efforts, am I indebted, and to 
whom I dedicate this book — my wife, Olive E. F. Tiffany. 

Flavei, B. Tiffany, A.M., M.D. 
Kansas City, April, 1894. 



PREFACE TO SECOND EDITION. 

■ When the first edition of this work was placed upon the 
market (now about a year and a half ago), it was with some 
anxiety upon the part of the author as to how it would be 
received by the profession, and what place it might take 
among the many kindred works already out. It is certainly 
gratifying to know that the book has been so pleasantly 
received. It is evidently filling a need, as the first edition is 
already exhausted. The second edition has been carefully 
revised, and contains some additional data and illustrations, 
together with some of the more recent developments. 

F. b. T. 

2457 Troost Avenue, Kansas City, Mo., 1896. 



PREFACE TO FOURTH EDITION. 

Six years have elapsed since the first edition of this work 
was placed on the market. This edition was exhausted in a 
little more than a year; then a second, and subsequently a 
third, were issued. Both of which being now used up, and 
still the demand continuing, we are impelled to issue a fourth 
edition, having gone thoroughly over the subject, eliminating 
some seemingly superfluous matter and adding other data 
thus bringing the book carefully up to date. 

F. B. T. 
October, 1900. 



Plate I. 




j& ». jpz&j'jg 



PROFESSOR VON HELMHOLTZ. 



Hermann Louis Ferdinand von Helniholtz, of Berlin, was 
born in Potsdam, August 31, 1821; studied in the Univers- 
ity of Berlin in 1838, as pupil in medicine and surgery; 
was graduated from the Frederick Wilhelms Institute in 
1842, with the inaugural thesis, entitled "De Fabrica 
Systematis Nervosi Evertebratorum"; under-surgeon in the 
Charite; 1843, army physician in Potsdam; returned in 1848 
as teacher of anatomy at the Academy of Arts and assist- 
ant at the Anatomical Museum at Berlin. Was called in 
1849 to the professorship of physiology and universal path- 
ology at Konigsberg, and in 1855 was transferred as profes- 
sor of anatomy and physiology at Bonn; from thence he 
went as professor of physiology to Heidelberg in 1858; in 
1871 at Berlin he accepted, together with the direction of 
the Physical Institute, a professorship of physics, with the 
character of Privy Government-Counsellor, and in 1883 was 
ennobled, which title he now bears. 

He belongs to the class of the Johannes Miiller's school. 
He became famous as a physiologist and established his 
calling with the work "Ueber die Erhaltung der Kraft" 
(Berlin, 1847), in which he for the first time seeks to show 
that all the transactions of nature obey the fundamental 
laws of mechanics. In the following year Helmholtz's activ. 
ity was turned to the physiology of the mind. But the in- 
valuable service he gave to human pathology and therapeu- 
tics through the invention of the ophthalmoscope, which 
entirely revolutionized ophthalmology, he made known in 
another work, "Beschreibung eines Augen-Spiegels zur 
Untersuchung der Netzhaut im lebenden Auge" (Berlin, 
1851). 

Among other worKS claiming our highest admiration, 
and in their special spheres pointing out new phases of 
science, are: "Handbuch der physiologischen Optik" (Eeip- 

li 



±& PROFESSOR VON HELMHOI/TZ. 

zig, 1856-66), in which his whole investigations upon the 
eyesight are laid down, and his book (now being revised 
by Dr. Arthur Konig, of Berlin), "Die Lehre von den Ton- 
empfindungen" (Braunschweig, 1862; 2d edition, 1865), which 
contains his acoustic investigations, displayed in collation. 
Besides, he has a large class of other works; for instance, 
Measurements of the Rapidity of Transmission of Nerve Irrita- 
tion; investigations upon articles on optics, acoustics, electric- 
ity teachings; manifold articles in journals; others in Muller's 
Archiv. (1845-48-50-52, etc.), Poggendorff's Annalen (of 1852 
et seq.), and Crelle's Journal of Mathematics; from Graefe's 
Archiv. (1855); also, such small works as "Ueber die Wech- 
selwirkung der Naturkrafte," etc. (Konigsberg, 1854), "Ueber 
das Sehen des Menschen" (Leipzig, 1855), "Populare Vor- 
trage" (2d part, Braunschweig, 1865-7) are published. His 
scientific treatises are together in two volumes (Leipzig, 
1881-83); his reports and discourses are also in two volumes 
(Braunschweig, 1884). 

The subject of this sketch, on the 8th of Sept., 1894, died 
at his home (Charlottenberg, near Berlin), in his 73d year. Dr. 
Knapp, who was a personal friend of Prof. Helmholtz, says in 
his obituary {Archives of Ophthalmology, October, 1894): "The 
allotment of his time for waking and sleeping, work and recre- 
ation, home-life and travel, was such as to make his labor in 
the highest degree efficient, and his life not only the most 
useful, but also most enjoyable and healthy. He hated to be 
annoyed by idlers and scientific pretenders. In the lec- 
ture-room he was always precise and unswervingly adherent 
to the subject, never being 'out of order,' despising jokes and 
stories to amuse his audience. He kept the attention of his 
listeners by the wealth of interesting facts and the clearness, 
precision, and elegance of his delivery. He was constantly in 
contact with his pupils, aiding and assisting them. . 
Taking him all in all, he was as near a perfect man as Nature 
has ever produced, the gift of the highest intellect combined 
with nobilitv of character and purity of life." 



Plate II. 





*/> 



// £(.C' 



BIOGRAPHICAL SKETCH OF PROF. DONDERS. 



The following brief oiographical sketch of Prof. F. C. 
Donders is a translation in part (by Olive E. F. T.) of a very 
beautiful tribute furnished by one of his disciples, our friend 
Le Docteur E. Landolt: 

"Since the death of Von Graefe ophthalmology has 
not met with a loss comparable to that which it has just ex- 
perienced in the person of Donders. It might be said that 
we do not lose the master, since his works remain and will 
always remain, forming the life, the soul of ophthalmology. 

"When, last year, his country, his pupils, his compatriots, 
his admirers from far and from near, united by one common 
sentiment of gratitude, changed into an apotheosis the re- 
treat from the professorship which the limitation of age im- 
posed upon him, Donders towered above the crowd who were 
deifying him, by his noble presence, the loftiness of his 
brow, the nobility and brilliancy of his look. 

"On this day, glorious among all days for him, in which 
every one rendered homage to his merits, he responded mod- 
estly: 'Talk not to me of my merits, but congratulate me 
on my lucky star.' 

"Donders was born May 27th, 1818, in Tilbury, Holland, 
of poor parents, the ninth child, the first son. It is said 
that the joy of having at last an heir killed his father. Of 
what supreme joy did fate deprive the father by taking him 
off at the cradle of his only son ! The mother watched over 
that cradle with a double solicitude, but although the heart 
of this great man always kept the impress of the cares of 
this tender mother, it is neither the society of his town nor 
the school of Duizel, where he learned La an and earned his 
living as sub-master until he was thirteen years of age, 
which can claim the honor of having dc-posited in him the 
germs of his future greatness. lie continued his studies of 
Latin in the school of Boxmeer until he was seventeen years 
of age. He became, consequently, very strong in this use- 



14 PROFESSOR DONDERS. 

ful language. He threw himself with great ardor into the 
medical sciences in the military school of Utrecht. In 1840, 
at twenty-two years of age, he occupied the chair of mili- 
tary surgeon at La Haye. The year 1842 saw him already 
the distinguished professor of anatomy and physiology in the 
same school of Utrecht which he had but just left as pupil. 

"Who would have said then that he would live sixty- 
seven years in this little city of Utrecht; that he would 
grow up in it and shine in it to such a degree as to make 
of this fireside of his activity a scientific center, benefi- 
cently radiating its light over the whole world, even after 
his death? What a brilliant epoch, moreover, was that in 
which Donders began to cultivate the fertile field of the 
sciences of man! 

"Schwann had just demonstrated the cell origin of all or- 
ganisms; Von Baer had just discovered the egg of mam- 
malians; Bischoff, the segmentation of the ovule; Henle had 
endowed science with his marvelous book of anatomy, nota- 
bly of microscopic anatomy; and the immortal Jean Miiller 
had opened new horizons to physiology by introducing into 
it the exact sciences. So emulation was not wanting in the 
new school, or rather in the school newly developing, which 
was illustrious with the names of Helmholtz, Briiche, Claude 
Bernard, and Ludwig. Donders was the worthy representa- 
tive of Holland in this noble phalanx. 

"There is not a domain in this vast science in which 
Donders has not left priceless traces of his labors. The life 
of tissues, circulation of the blood, digestion, secretions, 
movements, organs of senses, language, secrets of the nerv- 
ous system, were, turn by turn, explored by this indefatiga- 
ble seeker. He explained the formation of vowels, measured 
the rapidity of our thoughts, demonstrated the laws of evo- 
lution, of animal life, and the indestructibility of force. 

"If there is a crowd of facts, of laws, of theories,, which 
make illustrious his name, there are perhaps as many which 
we consider as belonging to science from all eternity, with- 
out knowing that we owe them to Donders. If the acquisi- 
tion of knowledge has more charm than the possession,. 
Donders found a joy still greater in its communication to 



PROFESSOR DONDERS. 15 

others. His first researches were published in the Neder- 
landsch Lancet, which he founded with Jansen and Eller- 
mann; also in the Hollandische Beitrdge, which he published 
in German with Van Dee and Moleschott, 1846. 

"What Donders preferred most of all was teaching viva 
voce, and what did he teach? Let us ask rather, what did 
he not teach? He possessed all the qualities which make 
the perfect professor : an erudition as profound as extensive; 
an excellent memory; an intelligence capable of adapting 
itself to his audience; a wit which colors abstract matters; 
a rich flow of language; a voice sonorous and flexible; 
gesture noble and significant; something sublime emanated 
from the man ; physically grand and beautiful, something at 
once imposing, captivating, and sympathetic; great knowl- 
edge, and great desire to impart it." 

As an instance of his great modesty we cite the reply 
made to one who attributed to him the discovery of astig- 
matism: "Pardon me, my friend, astigmatism was known a 
long time before my day; I only discovered astigmatic peo- 
ple." When a hospital and laboratory were needed in 
Utrecht, the name of Donders was already so well known, 
this prophet was so esteemed in his intelligent country, 
that he had only to lift his voice, to see gifts flowing in 
from all quarters sufficient for the creation of the two in- 
stitutions in which Holland has eternally honored herself. 

The following is the first account rendered by himself: 
"I have seen the unfortunate who had believed his exist- 
ence terminated by blindness thank God on seeing open 
before him a new period of happiness. I have seen the 
honest workman, once humiliated in eating the bread of 
charity, capable of earning again for himself and for his 
the savory bread of labor. I have heard the cries of joy 
of the young mother, who, long deprived of the sight of 
her child, could not turn away her eye with its new glim- 
mering light from her baby's face; and I have seen, in the 
child snatched from blindness and beginning to learn, how 
much nature is reflected the more willingly, and conse- 
quently the more divinely, in the eye of the child." 

There is no student of ophthalmology but is acquainted 



16 PROFESSOR DONDERS. 

with this sage and erudite teacher through his great work 
on Refraction, the source from which much knowledge is 
drawn by every writer on this subject. 

It was our good fortune to meet Prof. Donders in his 
home at Utrecht in the fall of 1887, and we shall never forget 
the warm welcome he gave us, strangers as we were. It was 
enough for this grand, noble soul to know that we had 
crossed the seas to meet and shake hands with our great 
teacher. It was indeed a proud and happy moment for us 
to sit and have communion with the great master — a bright 
spot in our lives that will never be forgotten. 

F. B. T. 



Plate III. 




**J \q**ma&$ 



EDMUND LANDOLT, M.D. 



It was at Washington, D. C, during the meeting of the 
"Ninth International Medical Congress of 1887, we first had 
the pleasure of meeting Dr. Landolt, who contributed much 
to the success of our section by his scientific communica- 
tions and his discussions. 

A few months later found us at No. 27, Rue Saint- 
Andre des Arts, Paris, where a few weeks were spent with 
pleasure and profit listening to his enthusiastic and able 
teachings, especially concerning the subjects of Refraction, 
of Insufficiency of the Ocular Muscles, and of Strabismus. 
Dr. Landolt may be called a specialist within the specialty 
of ophthalmology. He has contributed largely to this subject. 
His masterly work on "Refraction and Accommodation 
of the Eye" is regarded as authority by the student of to- 
day, as was £*nd is the work of Donders on the same sub- 
ject by all students. 

He was born in the town of Aarau, Switzerland, in the 
year 1846. To his early life passed in this picturesque 
country, in this beautiful scenic land of hills, lakes, and 
mountains, with clear, running streams, may be attributed, 
in a measure, his cheerful disposition and keen powers of 
observation. 

_ He studied in Heidelberg and Zurich. Received the 
degree of M.D. in 1869 at Zurich, and in 1875 at Paris. He was 
assistant surgeon to the surgical clinic in Zurich; later, surgeon 
to the ophthalmological clinics of the same university (Prof. 
Horner). Passed one year with Arlt in Vienna and Von Graefe 
in Berlin, another with Donders and Snellen in Utrecht. Visited 
the principal clinics in Germany, England, Italy, France; later, 
those of the United States of America. During the Franco- 
German War (1870-71) was surgeon-in-chief to the ambulance 
in Hericourt (France). Settled in Paris 1875. Organized, 
with Javal, the laboratory for ophthalmology at the Sorbonne. 

17 



18 EDMUND LAXDOLT, M.D. 

Among his principal works (over one hundred) are: 
"On the Retina," in Max Schultze's Arch., 1870. "Amblyopie 
hysterique," Arch, de physiol., 1 875. A manual of examination 
of the eyes, published in French and in English, 1879. A 
manual of ophthalmoscopy, published in French, English, 
Dutch, and Spanish. "Traite complete d'ophth.," with M. de 
Wecker, 4 volumes. "The Refraction and Accommodation of 
the Eye, 1886 (Edinburgh), 600 pages. "The Operation for 
Cataract in Our Time/' Arch, d'ophth. and Ophth. Record, 
1892. "The Anomalies of the Motor Apparatus of the Eyes," 
in "System of Diseases of the Eye," edited by Norris and 
Oliver (1893-4). 

Among the principal instruments invented by Dr. Lan- 
dolt are: Landolt's perimeter, ophthalmoscope, ophthalmo- 
dynamometer, forceps for strabotomy, double-bladed knife for 
discission. 

Dr. Eandolt is consulting surgeon to the Institution of the 
Young Blind in Paris. 



CHAPTER I. 



REFLECTION OF LIGHT. 



As reflection and refraction of light have to do 
with the anomalies of refraction and accommoda- 
tion of the eye, we shall briefly consider these 

phases of optics before en- 
tering upon the subject of 
ametropia. 

Light, by its action on 
the retina of the eye, ex- 
cites the sensation of vis- 
ion. The source of light 
may be natural or artifi- 
cial. The line in which 
light is propagated is called 
a luminous ray (RR, Fig. 1). 
A collection of parallel rays 
is called a beam of light 
(R'R'). A collection of divergent rays from a 
point is a pencil of rays 
(R"R"). 

In Figure 2 are rep- 
resented a few of the in- 
finite number of pencils 
of light emitted by three 
luminous points of a 
candl t flame. Every 
point of an illuminated 
object (ad) receives light 
from every luminous 
point of the candle flame 

21 





Fig. 2. 

Thus it follows that 



22 



REFLECTION OF EIGHT. 



every point in a luminous body is an independent 
source of light, and emits light in every direction. 
In a homogeneous medium, light is propagated 
in a straight line, but it changes its direction when 
it passes into a medium of different density. 

Images Produced by Small Apertures. If 
light from objects illumined by the sun — as trees 
or houses — passes through a small aperture and 
strikes a white screen, rays carrying with them the 
color of the points from which they issue will im- 
print their own color on the screen, and inverted 
images of the objects in their true colors will ap- 
pear upon it. This may 
be shown by holding in 
a darkened room a can- 
dle flame in front of a 
I cardboard, having a pin- 
hole in its center; the 
image will be projected 
■on the Avail. (Fig. 3.) 
Fig . 3 . The shape of the 

image is always the same as that of the object and 
is independent of the shape of the aperture. The 
inversion of the image arises from the fact that 
the luminous rays cross one another in passing 
through the aperture, the lower part of the object 
becoming the upper part of the projected image. 

When a luminous ray meets a polished surface 
it is reflected according to two laws: 

1. The angle of reflection is equal to the angle 
of incidence. 

2. The incident and the reflected ray are both 
in the same plane, which is perpendicular to the 
reflecting surface. 



11 



REFLECTION OF LIGHT. 



28 




Fig. 4. 

In Figure 4 let RO be an incident ray striking 
the polished surface AB at the point O, and OH 
the perpendicular erected at that point. The ray 
RO is reflected in the direction OR', making the 
angle HOR' equal to the angle ROH. 

Mirrors. A body with a polished surface that 
will show by reflection objects presented to it is 
known as a mirror. 

Mirrors may be either plane or curved; that is 
they have either a plane or a curved surface. 

Reflection from Plane Mirrors. MM 
(Fig. 5) represents a plane mirror. AB and HE 
are pencils of rays coming from the points A and 
H of the object AH. The reflected pencils BC and 
EC are divergent. The reflected rays entering the 
eye in the direction BC and 
EC are seen as if they came 
from ND. The position of 
ND can be determined by 
tracing backwards the lines 
of the pencils BC and EC un- 
til they meet. In the case 
of a plane mirror the image 
is as far behind the mirror 
as the object is in front of it, and is of the same 




24 



REFLECTION OF EIGHT. 



size a::d shape as the object. But the image is 
reversed, as can be demonstrated b}^ standing be- 
fore a mirror. The image of the right hand is 
on the left of the image in the glass. If the mirror 
is horizontal, with its reflecting surface upwards, 
and the object above it, the image will be inverted, 

as can be shown by placing 
a glass of water upon a 
looking-glass (Fig. 6). 

The image formed by a 
plane mirror is called a vir- 
tual image, as there can be 
no real image at the place 
where it appears, there 
being no reflected rays behind the mirror. 

When the reflected rays themselves meet, they 
form a real image. 




Fig. 6. 




Fig. 7. 



The surfaces of waters, when at rest, act as mir- 






REFLECTION OE EIGHT. 



25 



rors. Probably they suggested the mirror — 'twas 
the mirror of Venus and Narcissus. A body of 
water, for instance, when calm, will produce images 
of external objects, as of the moon, stars, buildings, 
etc. Figure 7 represents the phenomenon of such 
a reflection. In this case, it is the same as for the 
image formed by a horizontal looking-glass. 

Curved Mirrors. This class comprises those 
in which the reflecting surface is a portion of a 




Fig. 8. 

Ihollow sphere. If the concave side is used for 
reflection, it is a concave mirror; if the outer or 
convex side is employed, it is a convex mirror. 

In both concave and convex mirrors the middle 
point (A, Fig. 8) is the vertex of the mirror. The 
center of the sphere of which the mirror forms a part 
is called the center of curvature (C). A straight line 
(HK) drawn through the center of curvature and 
vertex of the mirror is called th principal axis of 
the mirror. 

Reflection 
from Concave 
Mirrors. A con- 
cave mirror may 
be considered as 
made up of an in- 
finite number of Fiff - 9 - 




26 REFLECTION OF LIGHT. 

small plane surfaces. All radii of the mirror, as 
CK, CI, and CA (Fig. 9), are perpendicular to the 
small planes which they strike. 

If C were a luminous point, all rays emanat- 
ing from it, and striking the mirror, would be re- 
flected back to C. 

Let L represent any luminous point. The rays 
LK and LI emanating from this point strike the 
mirror at the points K and I and are reflected to 
meet at a point /. The angle of incidence LKC is 
equal to the angle of reflection CK/, CK, the radius, 
being the perpendicular. Any other ray from L 
striking the mirror will be reflected to /. The 
rays before reflection are divergent, but after re- 
flection are convergent and meet. The place of 
meeting (/) is called the focus, and is the focus of all 
rays coming from the point L- It is obvious that 
rays emerging from the point / would come to a 
focus at L, since the angle of incidence and the 
angle of reflection would interchange, but still be 
equal. Two points in such relation, in which rays 
coming from one are focused at the other, are 
known as conjugate foci. 

If the luminous point L were nearer to C, the 
focus would also be nearer to C, as the angle of 
incidence would be smaller, and consequently the 
angle of reflection would also be smaller. 

If the point L is further removed from C, the 
angle of incidence becomes greater, which makes 
the angle of reflection correspondingly greater, and 
the point / approaches the mirror. If L is removed 
to an infinite distance, the rays would be almost 
parallel ; hence, rays may be regarded as practically 



REFLECTION OF LIGHT. 



27 




parallel when their source is at a great distance; 
e. g.y fixed stars. 

For practical purposes, we shall speak of the 
rays coming from a distance of 20 feet or more 
from the eye, as parallel, and call them infinite 
rays; while rays coming from a distance less than 
20 feet from the eye may be considered divergent, 
and these we shall designate as finite rays. 

Parallel rays striking a concave mirror become 
convergent by reflection, and meet at a point F 
(Fig. 10) in the 
principal axis. 
This point, which 
is called the prin- 
cipal focus of the 
mirror, is just half 
way between the Fig.io. 

center of curvature and the vertex of the mirror. 
On the other hand, divergent rays proceeding from 
the principal focus become parallel after reflection. 

Rays emanating from a point between the prin- 
cipal focus and the mirror (L, Fig. 11) will become 
divergent after reflection, and take the directions 
ME and NH. These lines 
cannot meet, and consequently 
there is no real conjugate fo- 
cus for L- But if the lines 
are prolonged backwards, they 
meet at a point. This point 
(/) where the prolongations Fig.n. 

of the reflected rays meet is known as a virtual 
focus, and the image resulting from these is analo- 
gous to those formed by plane mirrors. 

If the rays (previously rendered convergent by 




28 REFLECTION OF LIGHT. 

another concave mirror, or by a converging lens) 
strike the mirror in the direction of EM and HN 
in Fig. 11, they will come to a focus between the 
mirror and the principal focus, as at L. 




Fig- 12 

Reflection from Convex Mirrors. In con- 
vex mirrors, which may also be regarded as com- 
posed of an infinite number of small plane surfaces, 
there are only virtual foci ; for parallel rays, as HA 
and KB (Fig. 12), become divergent after reflection, 
and take the directions AM and BN, whose pro- 
longations backward meet in the principal axis at F 
and form a virtual focus; which in this case — the 
primary rays having been parallel — is half way be- 




Fig. 13. 

tween the center of curvature and the mirror, and 
is the principal virtual focus of the mirror. 



REFLECTION OF LIGHT. 



29 




If the rays come from a finite distance, as, for in- 
stance, point E (Fig- 13), a virtual focus (H) will be 
formed between the principal focus and the mirror. 

Images Formed by Concave Mirrors. 

1. If an object be held in front of a concave 
mirror, but at a greater distance from it than its 
center of curvature, an image is formed which is 
located between the principal focus and the center 
of curvature, and it is real, inverted, and smaller 
than the object. This is 
illustrated in Fig. 14. 

A pencil of rays from 
the point D in the object 
DE is reflected by the 
mirror, and comes to a fo- 
cus (D') in the secondary Fig. u. 
axis DB (which is a line drawn from any point of 
an object through the center of curvature); then D* 
is the conjugate focus of D and locates its image. 
The same explanation applies to E and all inter- 
mediate points of the object DE, and we have a real, 
inverted image at E'D', which may be projected 
upon a screen. The pencils of rays, after coming to 
a focus at E r and D', will, if prolonged, become 
divergent again, and the eye placed at a distance 
beyond the object will receive these divergent rays 
and will see the image of the object. This ac- 
counts for the fact that when we look into a con- 
cave mirror or reflector from a distance, we see a 
small, inverted image of ourselves in front of the 
mirror. This can be beautifully shown by using 
the head-mirror or the ophthalmoscope, such as is 
used for examining the throat or eves. 

2. The converse of the above needs no 



30 



REFLECTION OE LIGHT. 



separate explanation. The object is pla:ed at E'D', 
and its image is therefore at DE and may also be 
projected upon a screen. From this we deduce our 
second rule : The image of an object placed between 
the principal focus and the center of curvature is 
also real and inverted, but is larger than the object, 
and is located beyond the center of curvature. 

3. If the object be placed between the princi- 
pal focus and the mirror, the image is virtual, 

erect, larger than the 
object, and is back of 
the mirror (Fig. 15). 
DE is the object. 
The rays emanating 
from it become diver- 
gent after reflection, 
Fig .i 5 . and cannot come to a 

focus ; but their prolongations backwards form vir- 
tual foci, and thus make a virtual image. The 
lines CDD' and CEE' are secondary axes. From 




.<f T ^ — 




Fig. ir>. 



this we see how a person looking into a concave 



REFLECTION OF LIGHT. 31 

mirror, when being near it, will see an enlarged 
image of himself, as in Fig. 16. 

4. If the object be at the center of curvature, the 
rays will strike the mirror perpendicularly and be 
reflected back to the same point, and hence the 
image will coincide with the object, or, in reality, 
there is no image at all. 




Fig. 17. 

5. If the object be at the principal focus, there 
can be no image, as the reflected rays are parallel; 
and there can be no focus, as shown in Fig. 17- 
This can also be demonstrated by the head-mirror 
or the ophthalmoscope. 

Images Produced by Convex Mirrors. If 
we look into a convex mirror, we shall see a small, 
upright image of ourselves, which becomes larger 
as we approach the mirror, and smaller as we re- 
cede from it. If an 
object conies in con- 
tact with the mirror, 
the image is as large 
as the object. If only 
a part of the object 
Flgr ' 18, touches the mirror, the 

part that touches it will be of the original size, 




32 REFLECTION OK LIGHT. 

while the other parts of the image will be smaller, 
so that the entire image is deformed. 

Any image produced by a convex mirror is 
virtual. Fig. 18 shows how the image is produced. 

The rays after reflection are divergent and 
their prolongations meet in the secondary axes, 
producing the virtual image. 



CHAPTER II. 



REFRACTION OF LIGHT. 



A knowledge of the subject of refraction of 
light is of paramount importance in the adjust- 
ment of spectacles for the different anomalies of 
the eye. Without a knowledge of the laws gov- 
erning refraction, serious errors may arise in the 
attempt to correct these anomalies. Thus the use 
of improper glasses, whether chosen by the patient 
himself or selected by the jeweler, optician, or ven- 
der of spectacles, without scientific application of 
the laws of refraction, is liable to produce serious 
injuries. Frequently, the oculist finds hyperme- 
fcropes wearing concave glasses which were selected 
by some person possessing no scientific knowledge 
of optics, these glasses intensifying the anomaly 
instead of giving relief to the eye. The blame in 
such cases is usually attributed to the spectacles, and 
the patient naturally condemns spectacles in general. 

When a beam of light passes from one medium 
to another of different density, as from air into 
water, it is bent or refracted at the boundary plane 
between the media, unless it falls exactly perpen- 
dicular to this plane. If it passes into a denser 
medium, it is refracted towards the perpendicular 
erected at the point of incidence; if into a rarer 
medium, it is refracted away from it. 

Let AC (Fig. 19) represent the surface of a 
body of water, and #?E an incident ray striking it 
at an angle. It is refracted in the direction of E>/, 



S3 



34 



REFRACTION OF LIGHT. 




toward the perpendicular 
ED. If n'B be considered 
a ray passing out of the 
water into the air — a rarer 
medium — it is refracted 
from the perpendicular EB 
and takes the direction 
E#z. The angle wE3 is 
the angle of incidence, an- 
gle DE# is the angle of 
refraction, and angle nV^n* is the angle of deviation. 
In the circle with E as a center the perpendic- 
ulars oni and pn are dropped to the perpendicular 
BD; om is the sine of the angle m'EB, and pn is 
the sine of the angle DE/z. Now, suppose that the 
value of om is ft — i- e., it is fV of the radius Ew — 
and the value of pn is ft; then we have the sines of 
the two angles, one to the other as ft ' ft or as 4:3. 
The quotient f, obtained by dividing the sine of 
the angle of incidence by the sine of the angle of 
refraction, is called the index of refraction, i being 
the index of refraction of light in passing from 
air into water. In passing from air into glass 
the index is -f, and if 
the order is reversed, 
the reciprocal of these 
fractions must be taken 
as the indices ; that is, 
from water into air it 
is | and from glass into 
air it is f . The refract- 
ive index varies also 
with the color of the 
light. «*•«■ 




REFRACTION OF LIGHT. 35 

Cause of Refraction. It has been observed 
that the velocity of light is less in a dense than in 
a rare medinm. Let the series of parallel lines A 
and B (Fig. 20) represent a series of wave-fronts 
leaving an object C, and passing through a rectang- 
ular piece of glass DB. Every point in a wave- 
front moves with equal velocity as long as it 
traverses the same medium; but the point a of a 
given wave ab enters the glass first, and its veloc- 
ity is impeded, while the point b retains its origi- 
nal velocity; so that while the point a moves to 
a 1 ', b moves to b\ and the result is that the wave- 
front assumes a new direction within the glass- 
Again, the extremity c of a given wave-front cd 
first emerges from the glass, when its velocity is 
immediately quickened ; so that while d advances to 
d\ c advances to c\ and the direction of the ray is 
again changed, and it is parallel to its direction be- 
fore entering the glass. The eye placed at B sees the 
object as if it came from the other circle in the figure. 
If the light strike the glass perpendicularly, all points 
of the wave will be checked at the same instant on 
entering the glass, and hence will suffer no refraction. 
Effects of Refraction. Place a coin or 
fT some other object in the 
W bottom of an empty vessel 
p\p (preferably not transpar- 
^/T^ent) and at such a position 
that the coin shall just be 
hidden by the side of the 
vessel, as at B (Fig. 21). 
Fig. 21. Whilst in this position let 

water be poured into the vessel and the coin will 



Cc5 




36 



REFRACTION OF LIGHT. 



at once become visible at C. This is due to the 
refraction of the rays coming from the coin. The 
effect of refraction makes the bottom of the vessel 
seem higher than it is in reality. 

The ray from B after emerging at O is refracted 
in the direction OA, which makes the coin visible in 
the same line — i. e., at C in the straight line AOC 

Having described the principles of refraction, 
we shall now apply the same to prisms and lenses. 

Prisms. An optical prism is a transparent, 
wedge-shaped body. Fig. 22 represents a trans- 
verse section of such a prism. A is the apex or 
summit and MN is the base. 




Fig. 22. 



The ray LC on entering the prism is refracted 
towards CP, a perpendicular erected at the imping- 
ing point, and takes the direction CC; on emerg- 
ing, it is refracted from the perpendicular C'P' 
and takes the direction C'E. The point L appears 
as if it came from I. The rays are always refracted 
towards the base of the prism. It is essential that 
this fact be thoroughly fixed in the mind, as spec- 
tacles are in reality formed of prisms. 

Fig. 23 shows the manner of displacement caused 
by viewing an object through a prism. The object 
always appears deflected towards the apex of the prism. 

LENSES. Any transparent medium bounded by 
two curved surfaces, or one plane and the other 
curved, is a lens. 



REFRACTION OF LIGHT. 



37 




Fig. 23. 

Lenses are of two classes, converging and diverg- 
ing, according as they collect or disperse beams of 
light, 
prises 

1. 
2. 
3. 



Each class corn- 
three kinds: 

Class 1. 

Plano-convex. 
Donble-convex. 
Concavo-c onvex. 

{Convex- meniscus.) 

Class 2. 

4. Plano-concave. 

5. Donble-concave. 

6. Convexo-concave. 

{Concave meniscus.) 

Of these, the double- 
convex, double-concave, 
and meniscus are the ones 
mostly used as spectacles, 
and which we shall dwell 
on more particularly. 




3& REFRACTION OF LIGHT. 

The lenses just described are known as spher- 
ical lenses, because one or both of their surfaces 
forms part of a sphere. When the surfaces of 
a lens form part of a cylinder, it is known as a 
cyli7idrical lens. 

Cylinders. Cylindrical lenses are of great 
importance, and are much used for the correction of 
anomalies of refraction. Of late, they have been 
especially brought into requisition, and further at- 
tention will be given to them under the subject of 
astigmatism. 




Fig. 24. 

The bi-convex lens may be regarded as com- 
posed of two prisms placed together base to base, 
as in Fig. 24. 

The rays rr are refracted towards the bases of 
the prisms PP, and converge to meet at the point 
F, which is called the focus. If the rays are par- 
allel, this point is called the principal focus of the 
lens, and its distance from the lens is known as 
its focal length. 

The focal length of a double-convex lens is equal 
to the radius of the circle of which the curvature of 
the lens forms a part. The focal length of a plano- 
convex lens is equal to the diameter of the circle. 

In Fig. 25 the focal length of the double-con- 



REFRACTION OF LIGHT. 



39 



vex lens L is the radius DC, and parallel rays, as 
RR, will come to a focus at C The focal length 
of the plano-convex lens 1/ is the diameter AB, 
and parallel rays, as R'R', will come to a focus at A. 
The lens L is twice as strong as the lens L/. 




Fig. 25. 

A lens with a greater convexity than L will require a 
smaller circle, and hence a smaller radius, and will be 
stronger. It follows, then, that the shorter the focal 
length of the lens, the stronger is its power of 
refraction. 

A straight line, as AB (Fig. 26), perpendicular 
to both surfaces of any lens, and passing through 
its two centers of 
curvature, is called 
its principal axis. 

In every lens 
there is a point in 
the principal axis Fig 26 

called the optical center. Any ray that passes 




40 



REFRACTION OF LIGHT. 



through this point will, after emerging, assume 
the same direction that it had before entering the 
lens. A line drawn through the optical center 
from any point of an object is called a secondary 
axis, as AB (Fig. 27). 




Fig. 27. 

We have already stated that parallel rays striking 
a bi-convex lens become convergent after refraction, 
and meet at a point in the principal axis, called the 
principal focus. From this, it is obvious that 
divergent rays emanating from the principal focus 
as a luminous point may become parallel after 
passing through the lens, as shown in Fig. 28. 




Fig. 28. 

Rays coming from a point beyond the princi- 
pal focus at a finite distance are divergent, but 
will become convergent after refraction, and come 
to a focus, as in Fig. 29. 

Rays from S are focused at S r , and rays from 
S' would be focused at S. Two points thus re- 
lated — z*. e. y where rays from one are brought to a 
focus at the other — are called conjugate foci. 



REFRACTION OF LIGHT. 



11 




Fig. 29. 



Rays emanating from a point nearer the lens 
than the principal focus will be divergent after 
refraction, but the divergence will be less than be- 
fore they meet the lens, as shown in Fig. 30. 




Fig. 30. 

R is a parallel ray which has its origin in the 
principal focus (F), and becomes parallel by refrac- 
tion. SS are divergent rays originating in the 
point E, nearer the lens than the principal focus. 

Conversely, convergent rays (previously ren- 
dered so by another convex lens) striking a convex 
lens will come to a fo- 
cus at some point be- 
tween the principal 
focus and the lens 
thus, in Fig. 30, if we 
consider the rays SS 
as coming conver- 
gent towards the Fig. si. 
lens, they will meet after refraction ?t the point E. 




42 REFRACTION OF LIGHT. 

A double-concave lens may be regarded as com- 
posed of two prisms placed with their apices to- 
gether, as represented in Fig. 31. 

Parallel rays (rr) are refracted towards the bases 
of the prisms (PP), and thns become divergent. 
From this it will be seen that concave lenses have 
the property of dispersing or diverging parallel 
rays of light. If the rays rr were divergent, the}^ 
wonld become still more divergent after refraction. 
If we prolong the refracted rays backwards, they 
will meet at some point in the principal axis. 
This point (F, Fig. 32) is a virtual or imaginary 
focus; and if the incident rays have been parallel, 
this point is the principal virtual focus of the lens. 




Fig. 32. 

Convergent raj^s (previously rendered so by a 
convex lens), as rV (Fig. 31), may become parallel 
after passing through the lens. If the rays should 
be still more convergent, they would come to a 
focus at some place behind the lens. 

Formation of Images by Convex Lenses. If 
an object be placed in front of a convex lens, each 
pencil of rays coming from all points of the 
object, and meeting the lens, is brought to a focus 
somewhere behind the lens (providing that the 
object be outside of the principal focus). The as- 



REFRACTION OF LIGHT. 



43 



semblage of these foci makes up a picture of the 
object which is called its image. 

Images and their formation vary according to 
the distance of the object from the lens. 

1. Object at a distance greater than twice the 
focal length of the lens. The image in this case 
is beyond the principal focus, nearer the lens than 
the object, real, inverted, and smaller than the ob- 
ject. It is, of course, on the other side of the lens. 




Fig. 33. 



In order to explain the method cf the formation 
of the image, we may take any two points of an ob- 
ject, and if we take the terminal points, their foci 
will determine the place and size of the image. Let 
us take the points a and c in the object abc (Fig. 33). 
The line aa', passing from the point a through the 
optical center of the lens, is the secondary axis, and 
all rays emanating from a will come to a focus at 
some place in the secondary axis, as at a 1 '. This point 
is the conjugate focus of a\ for all rays coming from 
one of these two points will be focused upon the 
other. Similarly for c and all intermediate points, 
as b y for instance, which has its conjugate focus at U . 
Thus we have a real, inverted image. If a screen 
be placed at SS» a perfect image will be seen; but if 
placed either at S'S' or S"S", the image will be blurred. 

2. Object at a distance less than twice the fo- 
cal length, but beyond the principal focus. This is 
the converse of the above. The ima^e will be on 



44 REFRACTION OF LIGHT. 

the other side of the lens, further from the lens 
thaii twice the focal distance, larger than the ob- 
ject, inverted, and real. Fig. 3 4 illustrates this. 
AB is the object and ba its image. 




Fig. 34. 

3. Object at a distance equal to twice the focal 
length of the lens. In this case the image will 
be at a distance equal to twice the focal length 
behind the lens — z. £., as far behind the lens as the 
object is in front of it. The image will be of the 
same size as the object, real, and inverted. 




Fig. 35. 

In Fig. 35 F is the focal distance of the lens, 
and F' marks out twice the focal length. We see 
that the object and the image are both at a dis- 
tance of twice the focal length from the lens. 

4. Object at the principal focus. Rays of light 
proceeding from the principal focus, as we have 
already shown, become parallel after emerging 



REFRACTION - OP LIGHT. 45 

from the lens, and cannot meet. Thus no focus 
is formed, and no image can result. (Fig. 36.) 




Fig. 36. 

5. Object nearer the lens than the principal 
focus. We have already observed that rays com- 
ing from between the principal focus and the lens 
are still divergent after refraction, but less so than 
before meeting the lens. The refracted rays, 
therefore, cannot meet to form a focus; but if we 
prolong these refracted rays backwards, as shown 
in Fig. 37, their prolongations will meet, and form 
a virtual focus (H), which is on the same side of 
the lens as the origin of the rays, and further 




Fig. 37. 

away from the lens. An object, therefore, placed 
between the principal focus and the lens will have 
its image on the same side of the lens as the ob- 
ject, but farther away. The image is virtual, 
erect, and larger than the object; or, in other words, 
we have a magnified, erect image of the object, 



46 



REFRACTION OF LIGHT. 



which we can see by placing the eye on the other 
side of the lens, as in Fig. 38. 




Fig. 38. 

A convex lens nsed in this manner is called a 
simple microscope. 

The focns of a convex lens is a focns of heat as 
well as of light. If a paper be kept at the prin- 
cipal focus for a short 
time, the lens being 
exposed to the sun's 




rays, 



the 



paper 



will 



take fire. This prop- 
erty of lenses has been 
used to procure fire, 
and may be used for 
discharging a cannon; 
the lens may be so ar- 
ranged that the can- 
non is discharged at a 
certain time every day by the concentration of the 
sun's rays. (Fig. 39.) 

A lens used for this purpose is called a burn- 
ing-glass. 

(Strong cataract glasses are liable to injure the 
eyes if the person looks with them at the sun.) 
Compound Microscope. When it is desired 



Fis?. 39. 



REFRACTION OF LIGHT. 



47 



to magnify an object more than can be done with 
distinctness by a single lens, a componnd micro- 
scope is employed. This consists of a series of 
lenses — convex and concave, to correct spherical and 
•chromatic aberration — acting together as a convex, 
lens, the objective M (Fig. 40) ; and a convex lens 
as eye-piece (N). The objective forms a magnified, 
real image of the object AB at ba. The eye-piece 
magnifies the image ba to the size of b'a r . 




Fig. 40. 

Astronomical Telescope. The astronomical 
telescope consists essentially, like the componnd 
microscope, of two series of lenses; namely, an ob- 
jective O (Fig. 41), which forms a real, diminished 
image ba of the object AB, and an eye-piece E, 
which magnifies this image to the size dc. 




Fig. 41. 

Photographer's Camera, or Camera Ob- 
SCURA. Fig. 42 represents a vertical section of 
the camera. This consists of a box painted black 



48 



REFRACTION OF LIGHT. 



on the interior. A screen of ground glass S forms 
a partition in the box. A sliding tube T contains 
a convex lens L. If an object is placed some dis- 
tance in front (D), and the distance of the lens 
from the screen is suitably adjusted by means of 



B 


s 


T 


L 





■ 






A 









Fig. 42. 

the tube T, a distinct, real, and inverted image 
can be seen upon the screen by looking through 
the aperture C. When the image is properly fo- 
cused, the photographer replaces the ground-glass 
plate by a sensitized plate, and the chemical power 
of the sun's or "electric arc" rays paints a true 
picture of the object on this plate. 

Formation of Images by Double-Concave 
Lenses. Let AB (Fig. 43) represent an object; 

and MN a dou- 
ble-concave 
lens. The rays 
from A and B 
after refraction 
become still 

more diver- 
Fig. 43. T> 

gent. By pro- 
longing backwards the refracted rays, they meet 
at A' and B', forming there a virtual image. This 
image (A'B') is erect, smaller than the object, and 
nearer the lens than the object. This is always 
the case, whatever the distance of the object. The 
eye placed on the other side of the lens sees the 




REFRACTION OF LIGHT. 



49 




object nearer the lens than it really is, and the 

object appears smaller. 

Spherical Aberration. The angle AFB 
(Fig. 44), formed by drawing 
lines from the edge of the 
lens to the principal focus, 
is known as the aperture of 
the lens. 

As long as this angle is 
less than 10 or 12 degrees all 
parallel rays will meet at the 
Pi g . 44. principal focns, bnt if the 

angle is gr-eater, the rays which traverse the lens 

near the edge will be refracted to a point F (Fig. 

45) nearer the lens than the principal focus (G)* 

Rays pass- 
ing near the 

axis from A 

(Fig 46) come 

to a focus at F, 

while those 

passing near 

the edge of the 

lens cross the 

axis at F. Fiff - 45 - 

This wandering of the rays from a single focus 





Fig. 



is called spherical aberration. The evil may be 
largely corrected by interposing a diaphram DD\ 



50 REFRACTION OF LIGHT. 

provided with a central aperture smaller than the 
lens, so as to obstruct those rays that pass through 
the marginal part of the lens. 

Decomposition of Light. If a beam of sun- 
light pass through a prism, it is not only bent 
from its course, but is also decomposed into its 
various colors (Fig. 47), which together form the 
solar spectrum. It is due to the unequal refrangi- 
bility of the different colored rays, the violet being 
refracted the most and the red the least. The 
spectrum is composed of seven primary colors, oc- 
curring in the following order: violet, indigo, blue, 
green, yellow, orange, and red. 




Fig. 47. 

The colors of the spectrum are simple. If one 

color of the spectrum be allowed to pass through 

a hole in a screen and then fall on a second prism, 

it is refracted, but there is no change of color. 

Recomposition of Light. The colors of the 

spectrum may be reunited so 

as to produce white light. 

1. If it be acted on by a 
second prism exactly like the 
first with its refracting edge 
Fig. 48. turned in the opposite direc- 

tion, the light will be recomposed and will emerge 
as white light. (Fig- 48.) 




REFRACTION OF LIGHT. 



51 




Fig. 49. 



The emergent pencil E is parallel to the pencil 
S- This amounts to the same as passing light 
through a medium bounded by parallel surfaces. 
2. If the spectrum be received upon a concave 
mirror, it will be recomposed 
and a colorless image pro- 
duced. (Fig. 49.) 

The color of a body is due 
to the fact that it absorbs cer- 
tain colors and reflects or 
transmits others; thus, if a body absorbs all the 
colors except red, it appears red. Those that re- 
flect or transmit all colors in the proportion in 
which they exist in the spectrum are white, while 
those which transmit none are black. 

Chromatic Aberration. Light passing 
through a convex 
lens is decomposed 
as well as refracted. 
The tendency, there- 
fore, is to bring the 
more refrangible 
rays, as the violet, to 
a focus much sooner than the less refrangible rays, 
such as the red. This defect, which is most ob- 
servable in condensing lenses, is called chromatic 
aberration. 

Fig. 50 shows the violet rays coming to a focus 
at V sooner than the red ones at R. If these 
rays be received on a screen placed at mm, within 
the focus of the violet rays, a bright spot with a 
red border is seen-; if the screen be placed at ss, 
beyond the focus of the red rays, the bright spot 
has a violet border. (See Plate VII., page 126.) 




Fig. 50. 



52 REFRACTION OF LIGHT. 

The evil has been overcome very effectually by 
combining with the convex lens a plano-concave 
lens of a different substance. The convex lens is 
usually made of crown glass, and the concave lens 
of flint glass, as indicated in Fig. 51. 

Flint glass disperses light more than crown 
glass, and corrects the dispersion of the latter 

D without neutralizing all its refraction. A 
a compound lens composed of these two 
g lenses cemented together constitutes what 
is called an achromatic lens. In a similar 
Fig 51 way, the aberration is overcome in the 
eye by the combination of convexo-concave, dou- 
ble-convex, and concavo-convex; viz., cornea, lens, 
and vitreous body. 



CHAPTER III. 



THE EYE. 



The human eye (Fig. 52) consists, principally, of 
three investing tunics or coverings, three refrac- 
tive media, and three chambers. The tunics are : 

1. The sclerotic and cornea. 

2. The choroid, iris, and ciliary processes. 

3. The retina. 




Fig. 52. 

The refractive media are: 

1. Cornea and aqueous humor* 

53 



54 THE EYE. 

2. Crystalline lens and capsnle. 

3. Vitreous body. 
The chambers are : 

1. Anterior chamber. 

2. Posterior chamber. 

3. Vitreous chamber. 

The sclerotic (S) aud the cornea (A) form the 
external tunic of the eyeball; they are essentially 
fibrous in structure. 

The sclerotic or sclera is opaque and forms 
five-sixths of the covering of the globe. The 
cornea is transparent, having no bloodvessels, and 
forms the remaining one-sixth. The sclerotic, 
from its density and hardness, serves to maintain 
the form and integrity of the globe. 

The cornea, the watch-glass or window of the 
eye, consists of five la}^ers. It has no blood-vessels, 
but plenty of nerves and lymphatics. It serves to 
transmit light into the eye. It is convex in front 
and concave behind. Its curvature varies in dif- 
ferent individuals and is sometimes asymmetrical 
(astigmatic). The cornea also assists in focusing 
rays of light as they pass into the eye. 

The choroid (J 7 ) is the principal part of the 
second tunic, investing about five-sixths of the 
globe and consists of two layers, inner and outer. 
It is the vascular and pigmentary coat of the eye. 
The ciliary processes (H) are appendages of the 
choroid, being developed by a reduplication of its 
front part. 

The function of the choroid is to supply blood 
to the eye and act as a dark background, absorb- 



THE EYE. 55 

ing rays of light after they have passed through 
the refractive media to the retina. 

The iris (&) is a circular, muscular septum com- 
posed of circular and radiating fibres with fibrous 
stroma containing blood-vessels, nerves, lymphatics, 
and pigmentary cells. It has a circular aperture 
a little, to the nasal side of its center, called the 
pupil (P). The circular fibres are arranged around 
the pupillary margin, the radiating extend from 
the pupillary to the ciliary margin. The iris 
hangs vertically behind the cornea and in front of 
the crystalline lens. 

The function of the iris is to regulate the 
amount of light through the pupil to the eye, by 
the action of its circular and radiating fibres. 
The circular fibres contract to exclude and the 
radiating contract to admit light. 

The ciliary muscle (K) is placed at the junction 
of the sclera, iris, and cornea. This muscle consists 
of two sets of fibres, meridional and circular. The 
circular fibres of the ciliary muscle are believed to 
enter largely into the function of accommodation. 
(Further attention is given to this muscle under 
the chapter on accommodation.) 

The retina (jR) is the internal or third coat of 
the eye. It consists of ten layers, some of which 
are formed by the expansion of the optic nerve, 
from which the retina extends forward to the cil- 
iary muscle, where it terminates by a serrated mar- 
gin, the or a serrata. 

The layers of the retina from without inwards 
are as follows, as shown in the accompanving cut. 
(Fig. 53.) 



S6 



THE EYE. 



1. Pigmen t a ry 
layer (P). 

2. Layer of rods 
and cones, columnar 
layer, or Jacob's mem- 
brane (a). 

3. Membrana limit- 
ans externa (b). 

4. Outer nuclear 
layer (c). 

5. Outer molecular 
layer (d). 

6. Inner nuclear 
layer (e). 

7. Inner molecular 
layer (/). 

8. Vesicular layer 

9. Fibrous layer (k). 

10. Membrana lim- 
itans interna (i). 

Of these, the most 
important is the col- 
Flff,5S - umnar la} T er, or Ja- 

cob's membrane. Just at the center of the pos- 
terior part of the retina, at a point corresponding 
to the posterior pole of the axis of vision, about 
6 mm. towards the temporal side from the center 
of the optic nerve, is a yellow spot called the 
maada lutea, ox ye How spot of Sommerring (R, Fig. 
52). At the center of this spot is a depression 
known as the fovea centralis in which is found 
chiefly Jacob's membrane where the cones predomi- 




THE EYE. 



57 




Fig. 54. 



nate, as seen in Fig. 54 (V). At this point, the 
sense of vision is most acute. 

The space between the iris and cornea is known 
as the anterior chamber of the eye (B, Fig. 52) ; 
that between the iris and lens is the posterior cham- 
ber (L). These chambers are filled with a fluid 
known as the aqueous humor. The two chambers 
communicate through the pupil. 

The large chamber back of the lens is known 
as the vitreous chamber. It contains the vitreous 
body (D, Fig. 52), which forms four-fifths of the 
entire globe. This body is a gelatinous substance 
about the consistency of the white of an egg, and 
is enclosed in a thin, transparent membrane similar 
to the skin of an egg called the hyaloid membrane 
(G), and fills the vitreous chamber. It is hollowed in 
front for the reception of the crystalline lens. It 
is perfectly transparent, and serves to maintain the 
shape of the globe. It assists in focusing light 
upon the retina, and is a medium of nourishment 
to the crystalline lens. In foetal life it has a 
canal through its center through which passes the 
hyaloid artery to the back part of the lens. This 
artery occasionally remains and is seen after birth. 

The crystalline lens (C) is enclosed in a cap- 



38 THE EYE. 

sule, and is situated immediately behind the iris 
in front of the vitreous body; it is lodged in the 
concavity of the latter (the hyaloid fossa). The 
lens is a double convex body having its greater 
convexity on the posterior side. It is perfectly 
transparent and consists of several concentric lay- 
ers. It measures about 8.7 mm. in its transverse 
diameter, and about 3.8 mm. in its antero-posterior 
diameter, being about the shape of a small plum 
stone. It is the principal refracting medium of 
the eye. It is held in place by the suspensory liga- 
ment (NN), and is acted upon by the ciliarv mus- 
cle (K). 




Fig. 55. 

The optic nerve (E) does not enter the eye at 
the posterior pole of the axis of vision, but about 
6 mm. to the nasal side of this pole. It serves to 
transmit impressions to and from the brain. It is 
unimpressionable to rays of light, and the place of 
the entrance of the optic nerve is the blind spot 
of the eye. This can be demonstrated by the fol- 
lowing experiment : 



THE EYE. 59 

Cover the left eye, and direct the right eye 
steadily to the white star in Fig. 55. The circu- 
lar spot will also be visible, although less dis- 
tinctly, since it will be out of the direct line of 
vision (the sensibility of the retina diminishing as 
the image recedes from the yellow spot). Hold the 
page vertically at the height of the eyes, and at a 
convenient distance for seeing both objects in the 
above manner; now move it slowly backward or 
forward, and when a certain distance is reached 
the circular spot disappears, because its image has 
fallen upon the optic nerve or blind spot. Within 
and beyond this distance it is again visible. 

The eye may be likened to a camera obscura 
in which the retina serves as a screen or sensitive 
plate; the choroid as the dark background; the 
lens, aqueous, and vitreous as the refractive media; 
and the iris as a diaphragm to cut off those rays 
that would traverse the lens near its edge and 
give rise to aberration. The ciliary muscle acts as 
a sliding tube, or adjustment. 

If the two outer coatings are removed from the 
back part of the eye of an ox, recently killed, so 
as to render the eye transparent, true images of 
whole landscapes may be seen formed upon the 
retina of the eye looked at from the back, as in 
the kodak. 

The focusing of the image of distant or near 
objects upon the retina is effected by a change of 
convexity of the lens by means of the ciliary mus- 
cle. This change is known as accommodation. 
We can almost instantly change the convexity of 
the lens so as to form on the retina a distinct 



60 



THE EYE. 



image of an object miles away, or only a few 
inches distant. The nearest limit at which an ob- 
ject can be placed from the eye and form a dis- 
tinct image on the retina is abont five inches. 
The normal eye, in a passive state, is adjusted for 
objects at an infinite distance; as a fixed star (par- 
allel rays), and may be accommodated for objects, 
as above stated, at a distance of five inches. 

Dioptric System and Optic Axis. The refrac- 
tive media, namely the cornea, aqneons humor, 
crystalline lens, capsule, and vitreous humor make 
up the dioptric system. These media taken con- 
jointly, act as a bi-convex lens. The axis of the 
dioptric system is called the optic axis } the ante- 
rior extremity of which corresponds to the center 
of the cornea, and the posterior to a point situated 
between the yellow spot and the entrance of the 
optic nerve. 

Visual Link. The visual line is an imaginary 




Fig. 56. 
OC, Optic axis. F, Fovea centralis. VF, Visual iiue, N, Nodal point. 



THE EYK. 



61 



line drawn straight from the object through the 
nodal point N (Fig. 56), to the fovea centralis. It 
is not identical with the optic axis, and, according 
to Helmholtz, the visual line in front of the eye 
lies to the inner side of the optic axis and a lit- 
tle above; while its posterior extremity on the 
retina lies to the outer and lower side of the optic 
axis, or at the fovea centralis. 

Visual Angle. The visual angle (AOB and 
A'O'B', Fig. 57) is the angle under which an ob- 
ject is seen. It is formed by the secondary axes 
drawn from the extremities of the object to the 
nodal point. The larger the object the larger the 
visual angle, provided the distance be the same. 
The angle AOB is larger than the angle A'O'B'. 




Fig. 57. 

An object at a great distance (A'B') will form a 
smaller visual angle and hence a smaller image 
than the same object at a less distance (A"B""); 
therefore, the greater the distance the smaller will 
the object appear, and vice versa. 



62 THE EYE. 

U_E Fig. 58 shows that the small E at 

S four feet from the eye is seen under the 
same visual angle as the large E at 
twenty feet. This is the case with all 
£ intermediate letters; and the retinal image 

- of one is of the same size as that of the 
others. 

The smallest visual angle under which 

an object can be distinctly seen by the 

L! eye is one of 5' (five minutes), and this 

- has been taken as a standard for deter- 
mining the acuteness of vision. The 
test types of Snellen and Giraud-Teulon 
have been devised upon this principle, 

*-= each type being seen under an angle of 

"5 5' according to the respective distances; 

as for instance, No. 1 is seen under an 

angle of 5' at a distance of 1 foot. No. 

20 under the same angle at 20 feet, etc. 

p Nodal Point. The nodal point of 

> the eye is just in front of the posterior 

surface of the lens or where the visual 

and optic axes cross (N, Fig. 56). The 

axis ray passing through this point is 

not refracted; all other rays passing 



H 



w 




->- through it form secondary axes. 
Fig.58. Optic Angle. The optic angle (BAC 

and DEF, Fig. 59; is formed by the meeting 
of the prolongation outwards of the optic axes 
of the two eyes, the eyes being directed to the 
same point (fixation point). The angle becomes 
larger as the fixation point approaches the eyes 
(the optic axes converging). The angle be- 



THE EYE. 63 

comes smaller as the fixation point recedes (the 




Fig. 59. 



optic axes becoming less convergent). Angle BAG 
is larger than angle DEP (Fig- 59). 



CHAPTER IV. 



EMMETROPIA AND AMETROPIA. 



Emmetropic Eye. An emmetropic eye is an 
eye that is capable of focnsing parallel rays, or 
those from distant objects, npon its retina with- 
ont any effort of accommodation; or, in other 
words, its refraction is snch that when the eye is 
in a state of rest, parallel rays . (AA, Fig. 60) are 
bronght to a focns (F) upon its retina. This 
eye, according to Donders, is the ideal or normal 
eye (as to its refraction). 

If the rays come from a near point (C) they 
are divergent, and their focus would be at a 
point behind the retina (D); hence, the power of 
refraction of the eye must be increased in order 
to bring these divergent rays to a focus upon 
the retina. This increased power is brought 
about by the action of the ciliary muscle, which 
renders the lens more convex. (See "Accommoda- 
tion of the Eye," Chapter V.) 




Fig. 60.— Emmetropic Eye. 

An emmetropic eye is not necessarily a nor- 
mal eye, for it may be diseased and nevertheless 

64 



EMMETROPIA AND AMETROPIA. 



65 



be emmetropic; neither is an eye free from 
disease necessarily emmetropic, as an eye may be 
ametropic and otherwise healthy. 

Ametropic Eye. An eye that is not capable of 
focusing parallel rays upon its retina without an 
effort of accommodation is called an ametropic 
eye in contradistinction to the emmetropic. This 
condition is known as ametropia, of which we 
have two forms: myopia and hypermetropia. 

Myopia is that condition of the eye where the 
focus for parallel rays is in front of the retina. 

Hypermetropia, or hyperopia, is that condition 
where this focus is behind the retina. 

In the myopic eye parallel rays are united in 
front of the retina, but rays coming from a near 
object, being divergent, may be united on the 
retina. 

In myopia the eyeball is either too long or 
the state of refraction is too high, and rays com- 
ing from distant objects, instead of being focused 
upon the retina, unite at F (Fig. 61), cross and 
meet the retina as divergent rays, which form 
circles of diffusion (BB), and so give rise to a 
blurred and indistinct image of the object. 




Fig. 61.— Myopic Eye. 

In order to render the myopic eye capable of 
seeing distant objects distinctly, we place a con- 
cave lens before it, which diverges the rays, caus- 



66 



EMMETROPIA AND AMETROPIA. 



ing their focus to be further back, or upon the 
retina, as shown by the dotted lines (Fig. 61). 

In the hypermetropic eye, the refractive power 
is too low, or the eyeball is too short, so that 
when in a state of rest, parallel rays impinge 
upon the retina before coming to a focus, thus 
giving rise to circles of diffusion or blurred 
images of the objects looked at (Fig. 62). 

By placing a convex lens in front of the eye, 
the rays are rendered convergent before they 
enter the eye, and so their focus would be at a 
shorter distance than that of parallel rays, as at 
the retina. (R, Fig. 62 and dotted lines?) 




Fig. 62.— Hyperopic Eye. 

In an eye of a moderate degree of hyperme- 
tropia the same condition may be brought about 
by the power of accommodation, thus rendering 
the crystalline lens more convex (Fig. 63, dotted 

line). 

Angle Alpha. In 
the emmetropic eye, 
the visual line passes 
through the cornea 
slightly to the nasal 
side of its center, and 
meets the retina at 
the yellow spot. It 
crosses the optic axis 
Fig g3 at the nodal point 




EMMETROPIA AND AMETROPIA. 67 

(N, Fig. 64) and forms with it an angle of about 
5 degrees, which, is called the angle alpha (angle 
ONV), and when thus formed by the crossing of 
the visual line and the optic axis it is said to be 
positive. 




Fig. 64. 

Angle Gamma. C (Fig. 64) is the center of 
rotation of the eyeball ; angle OCV, formed by 
the optic axis and an imaginary line drawn from 
the object of fixation to the center of rotation, is 
called angle gamma. 

In the hyperopic eye the visual line lies more 
to the nasal side than in the emmetropic eye, and 
the angle alpha increases, being 8 or 9 degrees. 

In the myopic eye the visual line approaches the 
optic axis, and may coincide with it, or even lie to 
the temporal side, when the angle is said to be nega- 
tive. These differences in relation between the 
optic axis and visual line often give rise to an ap- 
parent strabismus, either divergent or convergent, 
as the visual line lies to the inner or outer side 
of the optic axis. 

Astigmatism. We have seen that in myopia 
the refraction is too great, while in hyperopia it 
is too low. This excess of refraction in simple 
myopia as well as the deficiency in simple hyper- 
opia is of the same amount throughout all the 



68 



EMMETROPIA AND AMETROPIA. 



different meridians of the eye (H, E, M; Fig. 65). 
There are eyes, however, in which one of the 
principal meridians is emmetropic, the other 
ametropic ; as for instance, an eye may be emme- 
tropic in its vertical meridian and ametropic in 
the horizontal, or vice versa] or both principal meri- 
dians may be ametropic bnt vary in amonnt. This 
inequality of refraction of the eye is called astig- 
matism (rays of light coming from a point and 
passing through the refractive media are not 
focused at a point). 




Fig-. 65. 

If the' eye is emmetropic in one meridian and 
myopic in the other, it is called simple myopic 
astigmatism (Sm, Fig. 65). 

If it is emmetropic in one and hyperopic in 
the other, it is called simple hyperopic astigmatism 
(Sh, Fig. 65). 

If it is myopic in one with a greater degree 



EMMETROPIA AND AMETROPIA. b\J 

of myopia in the other, it is called compound 
myopic astigmatism (Cm, Fig. 65). 

If it is hyperopic in one with a greater degree 
of hyperopia in the other, it is known as com- 
pound hyperopic astigmatism (Ch, Fig. 65). 

If it is myopic in one and hyperopic in the 
other, it is called mixed astigmatism (Ma, Fig. 65). 

If the eye is ametropic in only a portion or 
sector of a meridian, the condition is called 
irregular astigmatism, in contradistinction to the 
forms jnst enumerated, which come under the 
liead of regular astigmatism. Regular astigma- 
tism can be corrected by glasses ; irregular can 
not. 

Astigmatism is due to an asymmetry of curv- 
ature of one or more of the refractive media, 
usually the cornea. It may be of the lens. If of 
the cornea, it is called corneal astigmatism; if of 
the lens, lenticular. 

Astigmatism Common to all Eyes. In every 
so-called emmetropic eye the cornea is not pre- 
cisely symmetrical in its curvature, being slightly 
more convex in the vertical than in the horizon- 
tal meridian ; but the difference is very slight, 
and it is only where there is an appreciable vari- 
ation in the curvature that the eye is stigmatized 
astigmatic, and requires a correcting glass. 

Aphakia. An eye deprived of its crystalline 
lens, as after extraction of cataract, is said to be 
aphakic ; and if it is not of a high degree of 
myopia, it will require a convex lens to focus 
rays upon its retina — a stronger one for divergent 
rays or those coming from near objects, and a 



70 EMMETROPIA AND AMETROPIA. 

weaker for parallel rays or those coming from 
distant objects. 

Anisometropia. Occasionally, one eye is em- 
metropic while the other is ametropic ; again, we 
may have one form of ametropia in one eye, and 
another form in the other, or we may have the 
same form of ametropia in both eyes but differing 
in amount. This we call anisometropia. 



CHAPTER V. 



THE ACCOMMODATION OF THE EYE. 



If after looking through an opera or field glass 
at a distant object, it is desired to view one nearer 
at hand, it will be found impossible to obtain a 
clear vision of the latter unless the focus of the 
instrument is changed. This is effected by means 
of a screw. If a distant object be looked at by the 
naked eye through a veil or window screen near the 
face, it will be found that when the object is clearly 
seen, the fibres of the veil or wires of the screen 
are indistinct; and when the veil or window screen 
is looked at, the object appears blurred; in other 
words, distant and near objects are not seen with 
equal clearness at one and the same time. 

The eye has the power of adjusting itself for 
different distances, increasing its refraction when 
viewing a near object, and diminishing it when 
looking at a distant object. 

This power has been found by exclusion to be 
lodged in the ciliary muscle and is called the power 
of accommodation. 

The ciliary muscle of the eye might be likened 
to the screw in the opera or field glass; but in- 
stead of advancing and retracting the crystalline 
lens, as does the screw the lens in the opera or 
field glass, this muscle changes only the anterior 
portion of the crystalline lens. 



74 THE ACCOMMODATION OF THE EYE. 

The eye, by nature, is adjusted for distant ob- 
jects, and has to be accommodated for near objects. 
In the accommodation for near objects the lens 
changes its convexity and position, especially its 
front part. 




Fig. 66. 

In Fig, 66, the left half shows the position ot 
the parts when the eye is adjusted for distant ob- 
jects ; the right half when it is accommodated for 
near objects. 

When the eye is adjusted for distant objects, as 
shown in the left half of the figure, the pupil is 
larger, the lens is flatter, and the iris forms a curve 
(#); but when accommodated for near objects the 
lens advances, advancing the iris, the pupil be- 
comes smaller, the iris is straightened (5), and the 
anterior chamber is lengthened but shallower. 

In speaking of the anatomical structure that is 
brought especially into requisition in the power of 
accommodation, the ciliary body is the principal 
part; and this consists of two sets of fibres, cir- 
cular (CF, Plate IV) and radiating (ma) } besides 
the zone of Zinn (H'), and ciliary processes (P^). 



Plate IV. 




ANATOMY 

E. Retina. 

H, Hyaloid. 

Ro, Ora serrata. 

Cp, Pigment layer of cho- 
roid. 

Ch, Choroid. 

H*, Place of division of 
hyaloid. 

H'. Zonula. 

Pc, Ciliary processes. 

H". Posterior layer of 
hyaloid. 

CF. Circular fires of cili 
ary muscle. 

Z, Free portion of zonula 

cp, Canal of Petit- 



OF THE CILIARY REGION 

Lc, Capsule of lens. 

L. Crystalline lens. 

ha. Posterior chamber. 

va, Anterior chamber. 

S, Sclerotic. 

sc. Vascular layer of connec- 
tive tissue of the sclerotic 
conjunctiva. 

sc' . Its epithelium. 

ruci, Meridional fibres of cili- 
ary muscle. 

a. External fibres of mem- 
brane of Descemet. 

m. Middle fibres. 

i, Internal fibres, or ligamen- 
tum pectinatum.iridis. 



(WELLS i. 

csl. Canal of Schlemm. 

C, Cornea. 

cc, Its anterior elastic 
lamina. 

. Epithelium of the an- 
terior surface of the 
cornea. 

CD. Membrane of Desce- 
met. 

CD,. Place of division of 
membrane of Descemet. 

CDE. Epithelium of mem. 
brane of Descemet, I 

I, Iris. 

ip, Pigment layer. 



THE ACCOMMODATION OF THE EYE. 73 

The ciliary body is intimately connected with the 
cornea (C), sclera (S), iris (I), choroid (C^), and ret- 
ina (R). The radiating or meridional fibres blend 
anteriorly with the cornea and the ligamentnm 
pectinatnm iridis (*'), and posteriorly with the 
sclera ; while the circular fibres are more intimately 
connected with the iris, suspensory ligament (zone 
of Zinn), hyaloid membrane (H), and choroid; in 
fact, they are a part of the choroid. 

The *ciliary body is anchored at the limbus, or 
junction of the cornea with the sclera. The me- 
ridional fibres enter largely into the formation of 
the walls of the circular venous canal, or canal of 
Schlemm (csl). 

The zone of Zinn is a continuation of the hya- 
loid membrane which bifurcates a few mm. pos- 
terior to Schlemm's canal (at H*), the anterior por- 
tion traversing the ciliary body and passing around 
the front part of the lens, the posterior around 
the back part. Between the two layers and the 
lens is a triangular space traversed by fibres of 
both the anterior and the posterior portions of the 
zone of Zinn, producing an open meshwork or 
lacunae, similar to the spaces of Fontana (/, Fig. 69). 
This space has been designated the canal of Petit 
{cp). The posterior layer of the zone of Zinn is 
intimately connected with the retina at the ora 
serrata (R<?). 

The ciliary ligament is a narrow band of fibres 
encircling the iris at the junction of the cornea 
and sclera, to which is anchored the ciliary body 
by an intimate interlacing of the meridional fibres 
of the ciliary muscle. 



74 THE ACCOMMODATION OF THE EYE. 

The ciliary processes (P^) are from seventy to 
eighty in number. They constitute the inner por- 
tion of the ciliary body and are arranged in the 
form of a crown. In this crown is suspended the 
crystalline lens (L), which is held in place by the 
zone of Zinn (H" and Z). 

The ciliary muscle is' largely supplied by the 
ciliary nerves, which are very numerous and pass 
through the ciliary region to the cornea. The 
ciliary body is highly vascular; it is, in fact, largely 
composed of arteries, arterioles, veins, and venules, 
with a meshwork of pigmentary cells. 

The change in the form of the lens during ac- 
commodation has been considered to be due chiefly 
to the action of the circular fibres of the ciliary 
muscle (the movement of the iris being an asso- 
ciated movement). 

The conclusions in regard to accommodation 
according to Heinrich Muller are the following: 

1. "The circular fibres of the ciliary muscle 
exert a pressure upon the edge of the lens by 
means of which the latter becomes thicker. 

2. "The longitudinal fibres of the muscle 
cause an increase of tension in the vitreous humor 
on account of which the posterior surface of the 
lens is prevented from shifting, and the action of 
the peripheral pressure is chiefly confined to the 
anterior surface. 

3. "The pressure of the tense iris on the per- 
ipheral portion of the anterior surface of the lens 
probably assists in increasing the convexity of the 
latter. 



THE ACCOMMODATION OF THE EYE. 75 

4. "The arching forward of the center of the 
anterior snrface of the lens is rendered possible 
and favored by the recession of the peripheral por- 
tion of the iris, which is accompanied by a con- 
traction of the deeper (circular) layer of the ciliary 
muscle and the iris. 

5. "The contraction of the ciliary muscle 
causes finally a relaxation of the anterior portion 
of the suspensory ligament, by which means, again, 
the increase in thickness of the lens is promoted." 

It was formerly thought that the iris played 
an important part in the power of accommodation, 
but this was definitely disproved by a case in 
Von Grsefe's clinic in which the iris was entirely 
removed without disturbing in the least the power 
of accommodation. Also in congenital cases where 
no iris is present, the accommodation may be 
perfect. 

That the convexity of the anterior surface of 
the lens increases during accommodation for near 
objects may be proved by the " catoptric test," 
which is made as follows: 

Let a person in a room with dark walls direct 
his eye to some distant object and have a candle 
flame at one side of the eye so that its rays fall 
somewhat obliquely upon the cornea, say at an an- 
gle of about 30 degrees with the line of sight. 
The candle should be about 14 inches distant 
from the eye. If the observer place himself on the 
opposite side of the person observed, also at an an- 
gle of 30 degrees, three reflected images of the flame 
will become visible in the pupil, as in Fig. 67 (A). 

The first image (a) is the brightest and is re- 



76 THE ACCOMMODATION OF THE EYE. 

A T5 




Fig. 67. 

-fleeted from the cornea which acts as a convex 
mirror. It is virtual and erect. The second (6) 
is also erect and virtual, but is much fainter, and 
is reflected from the convex anterior surface of the 
crystalline lens, which also acts as a convex mir- 
ror. The third (c) is smaller, dim, real, inverted, 
and is reflected from the anterior surface of the 
vitreous humor, which acts as a concave mirror. 
If the person under observation now change his 
point of sight from the distant to a near object, 
the eyeball remaining fixed, the second image (6) 
becomes smaller, and places itself nearer the first 
(b'). This indicates that the anterior surface of 
the lens becomes more prominent, and approaches 
the cornea; but there is no change in the other 
two images, showing that the curvatures of the 
cornea and of the posterior surface of the lens 
remain unaltered. 

In Plate V, AA is the axis of the cornea and 
of the lens. The continuous lines of the lens 
show its form when adjusted for distant objects; 
the dotted lines show the form when accommo- 
dated for near objects. At F is the flame, and at 
O the eye of the observer These two are so 
placed that lines proceeding from them form equal 



Plate V. 




THE ACCOMMODATION OF THE EYE. 77 

angles with the axis when intersecting it at the 
same point. Therefore, the image of the flame 
reflected from the cornea is seen in the direction 
01, that from the anterior surface of the lens in 
the direction 02, and that from the posterior sur- 
face in the direction 03. These images projected 
on the surface II are seen as a, 6, and <f, as shown 
in the preceding figure (67, A). If the person 
under observation now change his sight from the 
distant to a near point, the anterior surface of the 
lens advances, as shown by the dotted lines, the: 
second image is seen in the direction 02' and pro- 
jected on the surface II appears at the point b V 
and has approximated the image a reflected from 
the cornea. This has also been observed in the 
preceding figure (B). 

The advance of the iris from protrusion of the 
anterior face of the lens in accommodation for 
near objects can be observed by looking into the 
eye from the side. The person under observation 
looks at some distant object, and the observer 
places himself in such a position that the edge of 
the iris is just concealed by the sclerotic. If the 
sight be now changed from the distant object to 
a nearer one in the same line of vision, the iris 
becomes visible a little in front of its former posi- 
tion. If the sight be again directed to the dis- 
tant object, the ciliary edge of the iris disappears 
behind the sclerotic. 

It has been claimed by j^ome that there is an 
active accommodation for distant objects, but at the 
present time it is believed that accommodation for 
distant objects is passive, while that for near ob- 



78 



THE ACCOMMODATION OF THE EYE. 



jects is active. The lens enclosed in its capsule is 
composed of elastic tissue, and possesses a high 




Fig. 68 — Hyperopic Eye. (Iwanoff.! 



degree of elasticity, by virtue of which it regains 
its normal form as soon as the pressure in the act 



of accommodation is relieved. 



Therefore, we con- 




Fig. 69.— Emmetropic Fye. (Iwanoff.) 

elude that the change in the form of the lens dur- 



THE ACCOMMODATION OF THE EYE. 



79 



ing accommodation for near objects is dne to active 
muscular force, while that for distant objects is a 
spontaneous reaction. 

Frequently, however, when looking at objects 
in the far distance, they are seen only very dimly; 
but by putting forth a great effort, looking in- 
tently, they finally come more distinctly into view. 
This would suggest an active muscular power for 
distant objects, or an increased retinal receptivity. 

We have seen that the circular fibres of the ciliary 
muscle play the most important part in the func- 
tion of accommodation, and they predominate in 
the hyperopic eye (Fig. 68) where the power of 
accommodation is constantly brought into use, 
whether the person is looking at near or distant 
objects. Fig. 69 shows the normal condition of the 
eye at the ciliary region; w' y Schlemm's canal ; f, 
Fontana's spaces; &, the cornea; J ) iris; d, liga- 
mentum pectinatum iridis; m, ciliary muscle; a! , 
epithelial layer of the cornea. 




Fig. 70.— Myopic Eye. (Iwanoff). 

In the myopic eye where there is little or no 
demand for the power of accommodation, the cir- 
cular fibres are almost wanting, as seen in Fig. 70. 

When the ciliary muscle is relaxed to its utter- 



80 THE ACCOMMODATION OF THE EYE. 

most, the lens has assumed its least convexity, and 
the eye is then adapted for its far point {punc- 
tum remotum) % 

When in this condition the eye is spoken of 
as being in a state of complete repose. 

When the circular fibres of the ciliary muscle 
have contracted as much as they can, the lens has 
assumed its greatest convexity, and the maximum 
amount of accommodation is in force; the eye is 
then accommodated for its nearest point. This is 
called the 'near point {punctum proximum). 

In the emmetropic eye the punctum remotum 
is situated at infinity. The position of the punc- 
tum proximum may be ascertained by noting the 
shortest distance at which the person can read No. 
1 of the small test type with each eye separately, 
(See test type, appendix.) 

In normal eyes the nearest point of distinct 
vision lies at about four or five inches from the 
eye. This varies according to the age of the per- 
son, the point receding from the eyes with advanc- 
ing years, or the waning of the power of accom- 
modation, beginning at the early age of ten ; at 
the age of seventy-five, the power of accommoda- 
tion is nil. 

For continued work at near objects, engraving, 
etc., the near point lies at about five inches. The 
furthest point of distinct vision in the normal eye 
is at an infinite distance. The distance between the 
punctum remotum and the punctum proximum is 
called the territory or range of accommodation. The 
greater this range, the more evidence of accommo- 
dative power. 



THE ACCOMMODATION OF THE EYE. 81 

Static Refraction is the refraction of the eye 
without the active accommodation; that is, when 
the accommodation is at rest, or when the eye is 
adjusted for distant objects. 

Dynamic Refraction is the additional refraction 
of the eye when the accommodation is brought 
into requisition, or when the eye is adjusted for 
near objects. If the maximum amount of dynamic 
refraction is exerted, the eye is adjusted for the 
punctum proximum. The sum of the dynamic and 
the static equals the maximum refraction of the eye. 

The difference between the maximum and the 
static refraction is the amplitude of accommodation y 
which is, in reality, the dynamic refraction. We 
thus have the formula a—m—s in which a repre- 
sents the amplitude of accommodation, m the max- 
imum refraction, and s the static refraction. 

MECHANISM OF ACCOMMODATION. 

The crystalline lens, in its normal state, is of 
an elastic nature and if uncontrolled tends to ap- 
proximate the spherical form; it, however, is un- 
der the control of the suspensory ligament, or zone 
of Zinn, which is tense when the eye is in a state 
of rest or adjusted for distant objects. By the con- 
traction of those fibres of the ciliary muscle which 
encircle the lens (the so-called circular fibres), the 
suspensory ligament becomes relaxed and the lens 
is allowed to assume a greater convexity, especially 
its anterior surface, and to advance towards the 
cornea. 

As a further proof of the change in the con- 
vexity of the lens during the accommodation of 
the eye for near objects or divergent rays, we may 



82 THE ACCOMMODATION OF THE EYE. 

mention the experiments of Hensen and Yoelckers 
on the lower animals, as the dog, cat, monkey, etc. 
They removed a part of the sclerotic in the ciliary 
region and thereby were able to perceive the con- 
traction of the ciliary mnscle which drew the cho- 
roid towards the cornea (the fixation point of the 
ciliary body). These experimenters also placed 
pins perpendicularly into the different parts of the 
choroid, and they noticed that the free ends of the 
pins swayed backwards as the ciliary muscle con- 
tracted, which shows that the choroid is advanced 
by the contraction of the ciliary muscle. They 
also introduced needles through the cornea and 
sclera, the point of the former resting on the an- 
terior surface of the crystalline lens, and that of 
the latter on the posterior surface of the lens (Fig. 
71). Then upon electrizing the ciliary muscle, the 

free extremity of the an- 
terior needle was carried 
backward, while that of 
the posterior needle was 
carried slightly forward. 
This would sho.w that 
the change of convexity 
of the lens in the act of 
accommodation is not 
entirely confined to its 
Fig71 anterior surface. 

Coccius noticed in patients with a large periph- 
eral iridectomy, also Prof. Hjort, of Christiania, 
in a traumatic case where the iris was entirely 
removed without injury of vision or accommoda- 
tion, that in the contraction of the ciliary muscle 
not only the choroid, but the retina advanced. 




THE ACCOMMODATION OF THE EYE. 83 

In studying the anatomy of this region and 
the mechanism of accommodation, one must observe 
how intimately associated is this ciliary body with 
the other parts of the eye, and the vast influence 
it has in producing the various affections and dis- 
eases, especially those peculiar to the uveal tract 
as well as those of the retina; and we may also 
fully appreciate the great comfort and relief ex- 
perienced when this power of accommodation is 
set at rest by a mydriatic, or relieved by the 
proper glass correcting the anomaly of refraction 
or accommodation. 

That a large per cent of headaches, so-called 
migraine, ciliary neuralgia, and even tic douloureux 
with many of the different forms of chorea, of hys- 
teria, of mania even, is due to some anomaly of 
refraction or accommodation, is recognized by the 
profession at large; and these patients, instead of 
haunting the doctor's office for many months or 
years, receiving little or no benefit, are now readily 
relieved by the scientific adjustment of glasses; 
thus, these glasses are not only permanently cura- 
tive, but they prevent more serious troubles, such 
as high degrees of myopia, detachment of the ret- 
ina, choroiditis, choroido-retinitis', neuro-retinitis, 
glaucoma, nervous prostration, hysteria, chorea, etc 



CHAPTER VI. 



HOW TO EXAMINE THE EYE. 



It is said that any one can administer treat- 
ment in disease if he knows the disease, and 
"there's the rub,'' for to know the disease — in other 
words, to correctly diagnosticate — one needs not 
only to be familiar with the symptoms in their 
various forms, but he must carefully examine ; and 
to examine carefully he must not only have the 
necessary means of examination and various tests, 
but he must know how to employ them. 

Successful physicians, to whom we look for 
accurate knowledge, from whom we gain valuable 
statistics, and who become eminent in the pro- 
fession, keep a full and accurate account of all 
cases brought under their notice. The doctor 
should record the name, age, nationality, birthplace, 
occupation, residence, color of eyes> temperament 
of each one of his patients, and then the history 
as gotten from the patient himself, if possible, not 
from the attendant. In many cases, as with children, 
the history has to be obtained from the parent or 
attendant. You may ask, Why take the color of 
the eyes and the temperament? Certain diseases 
seem to be peculiar to individuals of a certain tem- 
perament and color of the eyes. 

After having recorded the name, age, nation- 
ality, occupation, residence, history, etc., of the 



HOW TO EXAMINE THE EYE. 



So 



patient, proceed to examine the eyes, and record 
the amount of vision without, and then with the 
glasses. The principal test is that with the glasses 
from the trial case. (Fig. 72.) 

Test with Trial Lenses from Trial Box. 
The ordinary box of trial glasses (Fig. 72) contains 




Fig-. 



thirty pairs of spherical convex and thirty pairs 
of spherical concave glasses, ranging from 0.25 D. 
to 20 D.; eighteen pairs of cylindrical convex and 
eighteen pairs of cylindrical concave, ranging from 
0.25 D. to 6 D.; twelve prisms from 1° to 20°; some 
plain tinted glasses — red, green, blue, and smoked; 
■stenopaic discs with slots of various widths (A, Fig. 
73), also one disc with a circular opening (B); an 



HOW TO EXAMINE THE EYE. 




Fig. 74. 



HOW To EXAMINE THE EYE. 



8? 



opaque disc (C); a ground glass (D); and trial 
frames (Fig. 74), usually two pairs. To make the 
case more complete there should be a double prism 
for testing the strength of the muscles (A, Fig. 
75), as in heterophoria; a half-ground glass (B); 
a chromatic glass (C) ; and a disc with a rod which 
acts as a strong cylinder (D). 

In employing this test, first ascertain the 
amount of vision of each eye separately. Place the 
patient at twenty feet from Snellen's test type (a y 



E 

C B 

DLN 

P T £ R 

r Z B D K 

O F L C T C 



m 

it c a 

e r J e 



ill 

3 HI 

E W 3 
e a in m 



APEORTDZ 



ill 3 E PI m 



hi m e u a e 



u x t ro k 

00 i r 1 j 

p»»TVK»»»a*o lpMH| 

'•u.m.rn Queen & Co., Inc. «»■■■«« 

i b 

Snellen's Test Type. 

by or c) ) and see how far down the card he can read 
the letters. If he is unable to see the largest let- 
ter or character at twenty feet, lessen the distance 
between him and the card, stopping as soon as 
the largest letter comes into view. If the patient 
sees only the largest at ten feet, while he should 
see it at two hundred feet, his vision is ten two- 
hundredths. In testing for myopia, begin with 
weak concave glasses placed in the trial frames 
(Fig. 74), covering the eye not under test 



$8 



HOW TO EXAMINE THE EYE. 



with an opaque disc (C, Fig. 73). If, for instance, 
you begin with a — 0.25, — 0.50, or — 1 D., arid 




Fig. 75. 



this glass improves vision but slightly, try a 
stronger one, say — 1.50 D., or — 2 D., and so on 
until the greatest amount of vision possible is 
obtained by the glass. If there is a high degree 
of myopia, we do not expect to obtain, as a rule, 
twenty-twentieths, or perfect vision. If the amount 
of myopia is 10 D. or 15 D., frequently vision can 
not be brought to more than twenty-fiftieths. 
The weakest glass that gives the correction or 



HOW TO EXAMINE THE EYE. 89 

the highest amount of vision should be chosen; 
it is always best to under-correct slightly than 
to over-correct; for instance, if a — 6 D. will give 
twenty-fortieths, and it requires a — 8 D. or — 10 D. 
to get twenty-thirtieths, — 6 D. should be pre- 
scribed, rather than the higher number. If the 
glass is too strong, it brings into requisition the 
power of accommodation and produces muscular 
asthenopia, with liability to more serious compli- 
cations. 

If a convex glass improves vision for distant 
objects, hyperopia exists. Occasionally, a weak con- 
cave glass will also improve the vision in the 
hyperopic eye if there be spasm of accommodation; 
then a mydriatic may be necessary to reveal the 
real, true conditions. 

In testing for hypermetropia, each eye should 
be examined separately, as in myopia. Ascertain 
the amount by the strongest convex glass that 
will give the greatest amount of vision, which 
should be the glass prescribed. In hypermetropia 
there is always a certain amount of latent defect 
which subsequently will become manifest and a 
stronger glass will have to be prescribed. 

Frequently, astigmatism is associated with my- 
opia or hyperopia, and must be corrected by 
sphero-cylindrical glasses. The subject of astig- 
matism, however, will be carefully considered in 
Chapter IX. 

In testing the eyes, the examiner should ascer- 
tain for himself the true condition of vision, and 
not depend upon the statement of the patient; 
especially is this true with certain individuals. If 



90 



HOW TO EXAMINE THE EYE. 



you ask them whether they can see all the letters 
on the card, they will turn to you with an inquir- 
ing and almost injured look, and peremptorily 
declare that they can read every letter on the card; 
but if you screen one eye by the opaque disc and 
ask them to begin with the largest letter and read 
down, it is frequently found that they are unable 




Queen & Co., Inc. 



to call the letters correctly more than one-half to 
two- thirds down the card, showing that their vis- 
ion is perhaps not more than twenty-sixtieths or 
twenty- fortieths ; and even if they are able to see 
some of the letters further down, they will mis- 
call others, indicating astigmatism. 

To detect the presence of astigmatism, have 
the patient view the dial (Fig. 76) from a distance 
of twenty feet, and ascertain if he is able to see the 
lines, one set equally as well as another. If he is 
astigmatic, the lines in some special meridian will 



HOW TO EXAMINE THE EYE. 



91 



appear less distinct than in others, and this will 
indicate the meridian of astigmatism. 

To proceed with the examination, place a disc 
with a slot (Fig. 77) before the eye, rotate the slot 
into the meridian through which he can get the 
greatest degree of vision. If through this merid- 
ian he has perfect vision, say f#, then turn the 
slot to the opposite meridian. If it is the 90th 
that the vision is ■§#, turn it to the ] 80th — here, 
perhaps, it may only be |g, or more or less; 
then find the concave or convex glass that will 
give the highest amount of vision; if a concave 
glass, it is myopic astigmatism; if a convex glass* 
it is hyperopic astigmatism. 
If it be a case of compound 
astigmatism, both principal 
meridians are ametropic and 
will require a glass of differ- 
ent strength. If, for instance, 
when the slot is turned to the 
90° a glass of one dioptre is 
required to get -§£, and in the 
opposite two dioptres, then 
we have hyperopia of one D. 
and hyperopic astigmatism of Fig. 77. 

one D., requiring a spherical glass of one D. and 
a cylindrical glass of one D., with the axis of the 
cylinder in the 90th meridian. 

A case of mixed astigmatism can be worked 
out in like manner. If a convex glass improves 
vision when the slot is turned to the 180th merid- 
ian, and a concave improves when it is turned to 
the 90th, it is a case of mixed astigmatism with. 




92 



HOW TO EXAMINE THE EYE. 



hyperopia of the 180th meridian and myopia of 
the 90th, as in the following hypothetical case: 

We have 2 D. of hyperopia in the 180th merid- 
ian and 5 D. of myopia in the 90th. This might 
be corrected by giving crossed cylinders with the 
axis of each cylinder in the meridian we do not 




Fig 7 



wish to affect by the glass ; for instance, place a + 
2 D. cylinder with the axis in the 90°, and a — 5 D. 
cylinder with the axis in the 180°. Mixed astig- 
matism is usually corrected by a sphero-cylinder; 
as, in the above case, spherical +2 D. combined 
with a cylinder — 7 D., with axis in the 180°, might 
be prescribed; or we could use a spherical — 5 D. 
combined with +7 D. cylinder, axis of cylinder in 
the 90°. 



HOW TO EXAMINE THE EYE. 



93 



In prescribing glasses, the pupillary distance 
should be taken, and the glasses properly centered. 
A pupillometer (Fig. 78) for this measurement is 
convenient. 

Measurement of the Eye by the Kerato- 
SCOPE. The keratoscope (Fig. 79) is an instru- 
ment for measur- 
ing or examining 
the cornea. It 
was invented by 
Placido, and pre- 
sents an easy 
method of deter- 
mining if there 
is astigmatism of 
the cornea or not. 

The instru- 
ment is quite sim- 
ple, consisting of 
a card with several 
concentric rings 
an d a circular open- 
ing in the center. 

If the card 
with rings be held 
before the patient's 
eye, with his back 
to the light, the rings can be seen through the 
opening of the card reflected from the cornea; a 
convex lens of about 10 D. may be placed behind 
the card. If the cornea is symmetrical throughout 
its various meridians, the circles will appear cir- 
cular, as on the card. If there is astigmatism, they 







94 



HOW TO EXAMINE THE EYE. 



will be oval, and the direction of their longest 
diameter will indicate the meridian of astigmatism. 
The cylindrical glass that renders the ovals circu- 
lar will indicate the amount of astigmatism. This 
little instrument is a ready means of detecting and 
determining the amount of corneal astigmatism. 

Examination by the 
Prisoptometer. This 
instrument (Fig. 80) con- 
sists of a revolving dou- 
ble prism set in a large 
disc, divided by merid- 
ians of ten degrees 
apart, with indicator. 
There is a circular open- 
ing at the center of the 
instrument in which the 
prisms which have the ef- 
fect of doubling objects 
looked at are set ; and a 
white disc of four inches 
in diameter, as shown in 
Fig. 82, seen at a dis- 
tance of sixteen feet, is 
doubled, and if the per- 
son be emmetropic, the 
edges are tangent, as seen 
in a (Fig. 81). If the 
eye is myopic, the discs, 
instead of being tangent, overlap each other (<$), 
requiring a minus glass placed in the instrument 
to separate them so that their edges merely touch. 
This glass indicates the amount of myopia. If the 




HOW TO EXAMINE THE EYE. 



95 



eye is hyperopic, the discs will separate from each 
other (V), and the amount of hy- 
peropia can be approximately 
ascertained by the strongest convex 
glass placed in the clip required 
to make the two images tangent. 
If the prism in the instru- 
ment is turned, one disc revolves 
around the other, and if there is 
simple myopia or hyperopia, the 
images will maintain the same rela- 
tive position all the way around. 
If there is astigmatism, they will 
lap or separate according to the 
kind — myopic or hyperopic. 





Fig. 82. 



96 



LOW TO EXAMINE THE EYE. 



Examination of the Eye by the Ophthal- 
moscope. As a corroborative test, the patient 
should be examined in a darkened room by the 
ophthalmosccpe. 

By this instrument we employ three methods of 
illumination; namely, oblique, direct, and indirect. 

Oblique Method. By the oblique, or focaliza- 
tion, take a convex lens of two-inch focal power, and 



, , 


il 


,|| ,, - qjL 


; 


\ 





Fig. 83. 



focus a pencil of light upon the cornea and front 
part of the eye (Fig. 83). Place the patient in a 
chair with gas-light on a level with the pupil, and 



HOW TO examine: the eye. 



97 



about fourteen inches to one side, and a little in 
front of the patient. By focusing the light, thus 
causing it to flit over the front of the eye, any 
slight opacity of the cornea that may have escaped 
the naked eye is quickly discerned. By this 
examination, time is frequently saved, as these 
slight opacities simulate ametropia. 




Fig. 84. 



The ophthalmoscope was given to us by Helni- 
holtz in 1851, and up to the present time it 
has proven the greatest boon to ophthalmology. 
This instrument, especially in lower forms of 
ametropia, is one of the most reliable tests. For 
detecting and ascertaining the kind and amount 
of ametropia, Loring's ophthalmoscope (Figs. 84 



98 



HOW TO EXAMINE THE EYE. 



and 85), or a modification of this instrument, is the 
best. If we wish to recognize merely the anoma- 
lies and illuminate the fundus, Liebreich's ophthal- 




Fig. 85. 

moscope (Fig. 86), which is a much cheaper instru- 
ment, will suffice. 

Loring's ophthalmoscope contains a "tilting mir- 
ror and a large disc with a series of convex glasses 
on one side and concave on the other, with a zero 
between. The convex glasses range from 1 D. to 



HOW TO EXAMINE THE EYE. 



99 



k 7 D., the concave from 1 D. to 8 D. These can 
be rotated in front of the opening in the mirror. 
Besides the large disc, there is a segment of a 
disc containing a convex glass of 0.50 D. and 
one of 16 D., also a concave 0.50 D. and a con- 
cave 16 D. By adding the 0.50 to those of the 
large disc, we can readily get one or more whole 
dioptres with a half dioptre. With the pins 16 D. 
in front of the opening, we can, by rotating 




Fig. 86. 

the convex lenses in the large disc, get as high 
as 23 D. With the minns 16 D. in front of the 
opening, we can gain as high as 24 D. in a con- 
cave glass. 

The ophthalmoscope with the tilting mirror is 
an advantage, especially in determining the kind 
and amount of ametropia, as in this case you 
can hold the ophthalmoscope perpendicularly in 



100 



HOW TO EXAMINE THE EYE. 



front of the eye, and the light is reflected into the 
eye through the opening or sight-hole, with the 
lens behind it at right angles. The old-fash- 
ioned ophthalmoscope (Liebreich's^ must be tilted 







Fig. 87. 



towards the light, and if yon use a lens back of it,, 
you have to look through it obliquely. This not 
only increases the strength of the lens, but pro- 
duces an astigmatic effect. 






HOW TO EXAMINK THK EYK. 101 

Dr. Fox's ophthalmoscope (Fig. 87) is a modifi- 
cation of Loring's. The advantage claimed for it 
over Loring's is that it has a drive-wheel attached 
to the lower part of the instrument, which enables 
one to shift the lenses without removing the instru- 
ment from its position and without touching the 
face of the patient. 

With the ophthalmoscope one should learn to 
view the fundus with or without a mydriatic, and 
the first thing for a beginner is to familiarize him- 
self with the normal condition of the fundus and 
with its variations before attempting to measure 
the amount of ametropia or examine for diseased 
conditions. To see the fundus with its details, it 
is necessary to follow out a fixed, settled plan, 
and frequently it requires considerable time to be 
able to get a satisfactory view. One of the prin- 
cipal annoyances of the beginner is the bright 
spots or the reflex images from the dioptric media. 
These must be ignored in the examination of the 
fundus. 

With the ophthalmoscope we can quickly and 
definitively recognize the ametropic eye in its vari- 
ous forms and degrees. In the examination of the 
eye with the ophthalmoscope for the anomalies of 
refraction, there are two methods; namely, direct 
and indirect. 

Direct Method. By the direct method (Fig. 
88), we look directly into the e}^e examined by 
reflected light from a gas or lamp flame. The light 
should be placed at one side and back of the 
patient's head, say four or five inches to the side, 
and as many to the rear. The light should be on a 



102 



HOW TO EXAMINE THE EYE. 



level with the pupil. If the right eye is the 
one examined, the light should be placed to the 
right and rear of the patient's head; the observer 
should sit at the side of the patient, not in front, 




Fig. 



and look with his right eye. An adjustable chair 
or stool should be used, so as to bring the observer 
to the same height as the observed. Then, by 
means of the ophthalmoscope, reflect the light 
through the pupil into the eye. In this way, if 



HOW TO EXAMINE THE EYE. 103 

the media are clear, the whole fundus of the eye 
can be illumined, and one looks upon the retina 
and optic nerve. This is the only place in the 
whole body where the circulation of the blood is 
exposed to view. 

In order to see the fundus clearly, as in look- 
ing through a key-hole into an illuminated room, 
you have to come close to the pupil, even almost 
to absolute contact with the face of the person 
examined; then, by looking through, you get a view 
of the back part of the eye. 

In examining the left eye, the light should be 
at the left and rear of the patient. The observer 
should be seated at the left side of the person ex- 
amined and observe with his left eye (Fig. 88). Be- 
ginners, especially, are inclined, as a rule, to examine 
always with the right eye. This will not do ; if you 
examine the left eye with your right, it brings 
your face exactly in front of the patient's (nez 
a nez), the breath of each being inhaled by the 
other, which in many instances would be extremely 
unpleasant; besides, such a position does not ad- 
mit of the close proximity in this method neces- 
sary to gain distinct outlines of the fundus. Fig- 
ures 89 and 90 also show the direct method. 

By this method the fundus of the eye with its 
blood-vessels may be seen at some distance away, 
and by their appearance we are able to ascertain 
the different conditions of the eye, whether it be 
emmetropic, myopic, hyperopic, or astigmatic; 
for instance, if the fundus be viewed at four- 
teen inches, the light thrown into the eye by 
means of the ophthalmoscope, the blood-vessels 



104 



HOW TO EXAMINE THE EYE. 



of the eye under examination, upon the moving of 
the head of the observer, will seem to travel in a 
certain direction. In myopia they will appear to 
travel in an opposite direction from that in which 
the head of the observer is moved. If it be moved 

to the right, they will 
go to the left, and 
vice versa. The lat- 
ter is always a posi- 
tive proof of myopia. 
This is true with the 
ophthalmoscope hav- 
ing a concave mirror. 
In hypermetropia, 
the reverse is true. 
Here, the blood-ves- 
sels seem to move in 
the same direction 
that the head is 
moved ; if the head is 
moved to the right, 
they will go to the 
right, and vice versa. 
If it is a case of as- 
tigmatism, the ves- 
sels will be seen more 
distinctly in a certain 
meridian than in the 
Fig. 89. opposite one. 

In emmetropia, the observer has to approximate 
the observed eye in order to see the vessels dis- 
tinctly, and then, as his head is moved, the vessels 
behave as in hypermetropia. 







HOW TO EXAMINE THE EYE. 



105 



To Measure the Amount of Ametropia by 
this Method. The examiner must come near 
the eye of the patient, say within an inch of 
his face (Fig. 88). The power of accommo- 
dation of the eyes 
of both the patient 
and examiner must 
b e thoroughly re- 
laxed. This is eas- 
ier for the patient 
than for the exam- 
iner, as by the dazzle 
of the light thrown 
into the eye the pa- 
tient intuitively re- 
laxes his accommo- 
dation; however, this 
must not be wholly 
relied upon, but the 
patient's attention 
should be directed 
to a distant object. 
It is not so easy for 
the surgeon to relax 
his power of accom- 
modation. He is in- 
clined to look at the 
Fi s- 90 - fundus as from a 

near point, whereas he should view it as from an 
infinite distance ; for if he looks at it as from a 
near point with increased convexity of the lens,, 
his eye is temporarily myopic and would require a 
concave glass to see the details of the fundus clearly. 




106 HOW TO EXAMINE THE EYE. 

Many beginners make this mistake, believing 
that because a concave glass brings out the details 
sharper they have a case of myopia to deal with, 
whereas the opposite condition may obtain. 

The optic disc, i. e. y the optic nerve, is the first 
object to look for. Then a little to the temporal 
side about the same height, the yellow spot, and 
within the yellow spot a light dot, the fovea cen- 
tralis. The bright red reflex from the retina, il- 
lumined by its light pink disc, from the center 
of which the arteria centralis retinae and accom- 
panying veins radiate, the macula lutea with the 
fovea centralis, and the rich, mottled, granular 
appearance of the retina give a most beautiful 
picture. (Plate VI.) 

If the eye is a normal, emmetropic eye, the ret- 
ina will present a bright, rose-red, granular appear- 
ance, with a circular disc at the nasal side of its 
center ; and about six mm. to the temporal side of 
this, just at the center of the fundus, at the same 
height, will be seen a deep, reddened, or slightly 
orange shaded spot, the macula lutea, in the center 
of which is a light spot, the fovea centralis. 

The arteria centralis retina, or central artery 
of the retina, has two main branches, one ascend- 
ing and the other descending, both of which im- 
mediately give off numerous branches that radi- 
ate over the surface of and permeate the retina. 
The accompanying veins converge from the retina 
to the temporal side of the center of the disc, and, 
as a rule, pass over the arteries. 

This is the usual order ; sometimes it is re- 
versed ; occasionally, the arteries and veins will be 



Plate VI. 







HOW TO EXAMINE THE EYE. 107 

twisted one around the other, and present a sort 
of a corkscrew appearance. Not infrequently will 
be observed a pulsation of the veins near the cen- 
ter of the disc ; and also at this point the disc 
may.be cupped ; that is, appear deeper, giving some- 
times the illusive impression of arterial pulsation 
or glaucoma. Sometimes there is to be seen a 
slight crescent at the margin of the disc, usually 
at the nasal side, or, if not a crescent, occasion- 
ally a dark line of pigment may be seen, or small 
flecks or spots of pigment, both of which may be 
in a physiologically normal eye, not indicating a 
pathological condition. The arteries are lighter in 
color than the veins, and have a light streak 
through their center. More or less choroidal blood- 
vessels may be seen through the retina, especially 
in a dark-complexioned person, and the entire 
fundus presents a darker shade. 

In negroes, the contrast between the retina and 
the optic nerve gives the disc almost a white or 
slate-colored appearance, which might be mistaken 
for atrophy of the optic nerve; mulattoes have a 
rose-tint disc with a dark setting of the retina. 

If the eye observed by this close approximation 
be myopic, the fundus with its details will not be 
distinctly seen, and the disc will appear larger 
than the normal, the increase in size varying with 
the degree of myopia. As a rule, there will be 
seen a white crescent at the temporal side, varying 
in size. This crescent differs from the normal 
and denotes a pathological condition. The crescent 
is due to the thinning and giving way of the cho- 
roid and the retina, allowing the white sclera to 



108 HOW TO EXAMINE THE EYE. 

gleam through. This is one of the evidences of 
posterior staphyloma, or bulging of the eye back- 
wards, and it always impairs vision, varying in de- 
gree from a slight amount to nearly total destruc- 
tion. If the staphyloma is slight and stationary, 
especially in grown people, little is to be feared; but 
not so in the young, especially if it is progressing. 

In order to see the details of the myopic fun- 
dus distinctly, a concave glass must be placed in 
front of the eye, back of the mirror. In Loring's 
and similar ophthalmoscopes, as above described, 
there is a series of small lenses, concave and con- 
vex, which can be rotated in front of the eye. The 
weakest concave lens that will bring the blood- 
vessels and other details of the fundus distinctly 
into view will indicate the amount of myopia and 
the glass to be prescribed in the form of spectacles. 

To see the hyperopic eye, unless it be of a high 
degree, it is not necessary to use a convex glass; 
but if it be of a high degree, then a plus glass is 
necessary in order to see the vessels distinctly, 
and the strongest convex glass with which one 
can see the smallest vessels distinctly indicates 
the amount of hypermetropia. 

The part to be selected for the examination 
should be the margin of the disc at its temporal 
side, looking at the small vessels as they pass over 
the edge of the disc This is a delicate test, as it 
requires but a fraction of a D. to throw these blood- 
vessels at this point in or out of focus. Some 
surgeons prefer to examine the smaller vessels near 
the macula lutea instead of those at the margin of 
the disc, because the macula is at the posterior 



HOW TO EXAMINE THE EYE. 



109 



pole of the visual axis. In making this test it is 
absolutely necessary that all accommodation be put 
at rest and that the eye of the observer be emme- 
tropic. If not emmetropic by nature, it must be 
rendered so by a correcting glass, or allowance must 
be made for the ametropia. 




Fig. 91. 

In case of astigmatism, by the direct method, 
the disc, instead of being round, appears oval and 
its longer diameter may lie in any of the meridians. 

Indirect Method. By the indirect method we 
view the eye with the ophthalmoscope from a dis- 



110 



HOW TO EXAMINE THE EYE. 



tance of twelve or sixteen inches, and nse an 
intervening convex lens of two or two and a half 




Fig. 92. 



in. focal length (20 or 16 D.)» placed at its focal 
distance from the eye (Fig. 91). In this exami- 
nation the lens is held by the thnmb and index 



£&'. 



HOW TO EXAMINE THE EYE. HI 

finger directly in front of the pupil, and steadied 
by the little finger resting on the temple or brow 
of the patient. By this means an inverted image is 
seen in the air in front of the lens, which appears 
smaller and is sharper than by the direct method, 
especially with a weak convex glass of one to two 
D. within the ophthalmoscope. In using this test, 
the observer must bear in mind that the disc and 
all the details of the fundus are inverted and appear 
smaller. 

In using the indirect method, the size of the 
field depends upon the strength and size of the 
objective glass. If the pupil is dilated and a lens 
of plus 13 D. used, the diameter of the field will be 
about eight millimeters, or four times the area seen 
by the direct method. Fig. 92 illustrates the man- 
ner of making this examination. The lens L is 
the magnifying intervening lens producing an 
aerial image at F'H'. 

The inverted image of the disc produced by a 
convex lens at a certain fixed distance from the 
cornea is larger in hyperopia and smaller in myopia 
than in emmetropia. If the lens that is held in 
front of the eye is gradually withdrawn, the aerial 
image of the disc enlarges or diminishes according 
to the form of ametropia (myopia or hyperopia). 
If it does not change in size, it is a case of emme- 
tropia, as the rays issuing from such an eye are 
parallel and the image formed by the object glass 
will always be situated at its principal focus. If 
diminution takes place as the lens is withdrawn, 
it is a case of hyperopia, and the higher the hy- 
peropia the greater is the diminution. 



112 



HOW TO EXAMINE THE EYE. 



If the image is larger as the lens is withdrawn, 
the case is one of myopia. In astigmatism, as by 
the direct method, the disc, instead of appearing 
round, is oval, and if one meridian decreases while 
the other remains stationary as the lens is with- 
drawn, it is a case of simple hyperopic astigmatism. 
If the whole disc decreases in size, but one merid- 
ian diminishes more than another, it is a case of 
compound hyperopic astigmatism. An increase in 
one meridian, the other remaining stationary, indi- 
cates simple myopic astigmatism. An increase in 
the disc, but in one meridian more than in the 
other, indicates compound myopic astigmatism. 
If one meridian increases while the other decreases, 

the case is mixed astig- 
matism. 

The direct method has this 
advantage over the indirect, 
in that the parts all come 
out in their true position 
and the image is magnified 
several diameters. 

The indirect method has 
also its advantages. It 
gives a larger field, and by 
this method we are able to 
make a more rapid exami- 
nation of the whole fundus. The direct method 
gives a smaller field, but greatly magnified, and any 
slight abnormality, change, or defect of the fundus 
will be detected by this method, whereas it might 
be overlooked by the indirect. 

The blood-vessels of the emmetropic eye should 




Fig. 93. 



HOW TO EXAMINE THE EYE. 



118 



be easily seen without the aid of a lens, especially 
at a near point to the eye. 

Appearance of the Fundus by the Direct Method. 
In people of dark complexion the fundus of the 
eye has a slightly granular appearance, while in 
those of light complexion the fundus shows its 
choroidal vessels with lighter-colored interspaces. 
People with neither very light nor dark complex- 
ion have a fundus in which the choroidal vessels 
appear large with dark-colored interspaces. 

The macula lutea is about six mm. from the 
center of the optic disc and is darker in color, hav- 
ing a light spot in the center, the fovea centralis. 

The optic nerve (Pig. 93) is from one and one- 
half to two mm. in 
diameter, and is 
much lighter in color 
than the surround- 
ing retina. It has 
a light pink-r o s e 
tint. There is usu- 
ally a slight depres- 
sion in the center, 
called the " physio- 
logical CUp" (C). Fig. 94. (Noycs.) 

The optic disc has a well-defined margin where 
the choroid joins the nerve, frequently with some 
traces of pigment, known as the choroidal ring (A). 

The sclerotic ring (B) is a light circle within 
the choroidal ring. 

Sometimes the hyaloid artery is seen projecting 
into the vitreous body; occasionally it extends quite 
up to the posterior surface of the lens, or it may 




114 HOW TO EXAMINE THE EYE. 

advance nearly np to the lens and then turn back, 
coiling about itself and dipping down into the 
retina (Fig. 94). 

Enlargement of the Ophthalmoscopic I?nages and 
How to Determine the Amount The nearest dis- 
tance at which we can distinctly see an object is 
from four to five inches from the eye, and when 
the object is approximated to the eye until it is 
one or two inches distant, the image is blurred and 
indistinct; but when we examine an eye with the 
ophthalmoscope, we can generally get a better view 
of the fundus by coming almost into contact 
with the eye examined. The eye being about one 
inch in diameter, the examined fundus is conse- 
quently not much more than an inch distant from 
the observer's eye, and yet we are able from said 
distance to obtain a clear and well-defined outline 
of the fundus and its details, whereas an}^ external 
object could not be seen with distinctness at such 
a short distance without the aid of a converging 
lens; and so it would be impossible to see the 
fundus of the eye were it not for its refractive 
media, which act as a bi-convex lens, and magnify 
the image of the fundus. Hence, it must be borne 
in mind that when looking into the eye through 
these media by means of the ophthalmoscope 
everything seen at the fundus is enlarged at least 
five or six times its real size ; but as the fundus 
is viewed through the refractive media of the eye 
and all images or objects are seen magnified, we 
come to look upon them from their apparent size 
and relation one to the other, rather than from 
their real size and condition. For instance, instead 



HOW TO EXAMINE THE EYE. 115 

of regarding the optic disc as less than two mm. 
in diameter, we look upon it as being as large as 
the ball of the finger, or about ten mm.; and so 
with the distance of the fovea centralis from the 
optic disc, instead of about six mm., we think 
of it as being twenty or thirty mm. away. The 
same with any foreign body that may be lodged 
in the retina; it appears much larger than it really 
is, and at a greater distance from a given point 
than its real distance. Therefore, it is of practi- 
cal importance that we be able to determine at 
once the real size, or, what amounts to the same 
thing practically, the magnification. Dr. Landolt 
has from accurate calculation and experiment 
demonstrated that the image at the fundus of the 
eye by the direct method projected thirty centi- 
meters will be magnified just twenty times its 
real size. 

To facilitate the measurement and to make the 
same a matter of record, I have arranged a tablet 
which is checked off into squares by parallel lines 
five mm. apart (page 116). The tablets come in 
sets of two, one for each eye. They are to be 
placed just thirty cm. or one foot back and to one 
side of the plane of the patient's iris, the one for 
the right eye being placed to the right of the 
patient, and that for the left to the left of the 
patient, so that when examining the right eye your 
left will be in front of one tablet, or if examining 
the left the other tablet will be opposite your right 
eye. The tablet may be attached to the wall or to 
the back of the patient's chair. The center of the 
tablet should be at the same height as the pupil. 



116 



HOW TO EXAMINE THE EYE. 



..19. 



Name age. 



MAP of the magnified image of the fundus of 
the eye as seen at a distance of thirty cm. 








10 




20 




30 


40 • 


50 


60 




'0 


80 






1 






















1 


c 
































































8 




























i 














| 


















c 














1 






















1 








| 
















c 












| 








i 
i 














1 














f 






g 


| 






1 


























1 














| 






s 


1 




















I I 


































c 


































































s 
































































c 




































































8 












1 " 




















































© 
































iH 
































8 



























The size of the tablets is T by 11 inches* 



HOW TO EXAMINE THE EYE. 117 

To project the picture of the fundus of the 
right eye, sit at the right side of the patient and 
view the eye with your right, looking at the tab- 
let with your left. To examine the left eye, sit at 
the patient's left side and examine with the left 
eye, looking at the tablet with your right. 

At first, it is difficult to project the picture of 
the fundus and see it on the plaque, but a little 
practice will soon bring it out. If examining the 
right eye, ask the patient to look slightly to the 
left and view from the nasal side; that is, look 
from within outwards. At first, you will probably 
see the picture on the cheek or temple of the 
patient; if then you ask the patient to look slightly 
more to the left, the picture will shift from the 
face to the plaque, and at this distance of thirty 
•cm. it will be magnified just twenty times its real 
size. Thus it is easy to determine at once the 
size, relation, and distance apart of all parts of 
the retina. For instance, if the diameter of the 
optic disc be two mm., the diameter of its pro- 
jected image on the tablet will be about forty mm., 
or the length of eight squares, and hence will 
occupy the circular space of nearly sixty-four small 
squares, or four large squares. 

Again, if the distance from the center of the 
disc to the center of the macula lutea be six mm., 
then the distance on the tablet should be 120 mm., 
or the length of twenty-four small squares. 

A tracing with pencil of the details of the fun- 
dus as the picture is projected upon the plaque 
can be readily made, showing both normal and 
abnormal conditions as to size, position, relation, 



118 HOW TO EXAMINE THE EYE. 

etc; for instance, any foreign body lodged on the 
retina can be located and its size estimated ; scoto- 
mata, hemorrhagic or pigmentary spots mapped 
ont; and then the page can be torn off and filed 
away in the record book for future reference. 

It will be readily seen that this tablet is very 
useful to the oculist, as it is accurate, easily 
employed, and a valuable aid to diagnosis. It 
is also valuable as a record, having, besides the 
picture of the projected fundus, the name and age 
of the patient, as well as the date of the examina- 
tion, space for which is left at the top of each 
page. 

The value of this plan of gaining data is so 
obvious as to need little more than mere mention, 
and it is of such practical value as to recommend 
itself to all painstaking and careful observers. 

Shadow Test, Retinoscopy, Keratoscopy, 
Pupilloscopy, Skiascopy. This test, which is very 
valuable as an auxiliary, is especially usetul in 
the examination of the eyes of children, as well as 
of those people whose statements are not to be 
relied upon. It is especially advantageous in the 
examination of children, as it is difficult to get 
them to fix an object (in the examination with the 
ophthalmoscope they invariably want to look at the 
instrument or at your eye). 

In the shadow test, the kind of refraction is 
determined by the direction of the shadow in the 
pupil cast by the reflection of light from the retina. 
The patient should be placed in a darkened room, 
with a lamp, gas, or electric light immediately above 
his head. The operator should be at least a meter 



HOW TO EXAMINE THE EYE. 



119 



away, and with a plane mirror he should reflect the 
light into the eye (Fig. 95). The pupil should be 
dilated, with the power of accommodation at rest. 
With the flat or plane mirror, reflect the light into 
the eye. This will produce a shadow of the fundus 
in the pupil; and this shadow is made to change 
its position by simply tilting the mirror. In the 



I 



; :t:f 




Fig. 95. 

emmetropic, hyperopic, or very slightly myopic 
eye, the shadow will flit across the pupillary area 
in the same direction that the mirror is tilted. 
This shadow appears at the edge of the cornea, 
and, according to the amount of tilting or rotation 
of the mirror, advances from the edge over or across 
the pupil. In the emmetropic eye the shadow is 



120 how to examine the eye. 

very dim, and requires but a very weak gla*3 
to reverse its direction. In the hyperopic eye 
the shadow is more distinct. In the myopic eye, 
if the degree of myopia is less than 0.25 D., the 
shadow goes in the same direction as in hyper- 
opia and emmetropia. If the degree of myopia is 
more than 0.50 D., the shadow produced will travel 
in the opposite direction from the way the mirrot 
is tilted. If the mirror be tilted from above down- 
ward, the shadow will creep up from below and 
pass off at the upper part of the pupil, and vice 
versa; if the mirror be tilted from the temporal 
to the nasal side, the shadow will creep over from 
the nasal to the temporal, and vice versa. 

With the plane mirror the method is more 
simple than with the concave (the one ordinarily 
nsed with the ophthalmoscope). If the concave 
be nsed, we have a reversed condition; i, e. } in the 
emmetropic, hyperopic, or slightly myopic eye, the 
shadow will travel in an opposite direction from 
which the mirror is tilted; and in the stronger 
myopic ic will travel in the same direction. 

The accompanying figure (Fig. 96), as given by 
Nettleship, will explain these phenomena. 

"With a plane mirror, the source of light for 
the observed eye is an erect and virtual image of 
the flame formed at the same distance behind the 
mirror as the lamp is in front of it. In Fig. 
96, 1, this image is at /, the virtual focus of L. 
A second and inverted image of / is formed on 
the retina of an emmetropic eye at I. When the 
mirror M is rotated to M', / will move in the 
opposite direction to /', but its retinal image I will 



HOW TO EXAMINE THE EY^. 



i21 



move to I'; that is, in the same direction that the 
mirror is rotated; or, in other words, it moves 




Fig. 96. (Nettleship.) 

with the mirror. These movements of / and I oc- 
cur in every eye, whatever its refraction. In eniine- 
tropia and in hypermetropia the movement of the 



122 



HOW TO EXAMINE THE EYE. 



retinal image is seen as it occurs (and therefore 
is said to move with the mirror^ but in nryopia 




Fig. 97— Fournet's Refractometer. 

(Fig. 96, 2) the observer sees an inverted image of 
I formed at the far point of emmetropia, and its 



HOW TO EXAMINE THE EYE. 



123 



movements are exactly the reverse of those of the 
retinal image; therefore when, on rotating M to 
M', I' moves to I 2 , the image V 1 seen by the ob- 




Fig.98. 






server moves to I' 2 ; that is, against the mirror. If 
the plane mirror be used at a distance of more 
than one metre, say four feet, from the patient, a 
movement of the shadow with the mirror will 



124 HOW TO EXAMINE THE EYE. 

occur in myopia of 1 D. or less, but if the observer 
be two metres away, the characteristic movement 
against the mirror will be obtained, unless the 
myopia be less than 0.50 D." (Nettleship.) 

To ascertain the degree of ametropia, the box 
of trial glasses with trial frames may be em- 
ployed. Adjust the trial frame to the patient's 
face, covering the eye not to be tested, with an 
opaque disc. If it is a case of myopia, place from 
the trial box a weak concave glass in front of the 
eye; then, if on tilting the mirror the shadow still 
continues to travel in an opposite direction or 
against the mirror, employ a stronger glass, and so 
continue until the shadow is dispelled or reversed. 
If the glass cause the shadow to travel with the 
mirror, it shows that the myopia has been over-cor- 
rected. In hyperopia a convex glass must be used, 
beginning with a weak one and continuing with 
stronger ones until the shadow is dispelled. If the 
shadow is caused to travel against the mirror, it 
shows that the Iryperopia has been over-corrected. 
The glass that will dispel the shadow, or slightly 
turn it with the mirror, will indicate the amount of 
hyperopia. Different forms of astigmatism can in 
a similar way be ascertained. Instead of the trial 
glasses from the box, Fournet's compound ophthal- 
mic refractometer (Figs. 97 and 98) or Bull's 
optometer (Fig. 99) can be used, one eye being 
covered by an opaque disc; then rotate before the 
eye being tested the large disc carrying concave 
or convex glasses, according to whether it be 
myopia or hyperopia to be corrected. 

Chromatic Test. This test is based upon 



HOW TO EXAMINE THE EYE. 



125 



chromatic aberration. As has already been noticed, 
a prism separates white light into the different 
prismatic colors: red, orange, yellow, green, blue, 
indigo, and violet. The red is the least deviated 
from its primitive direction, blue and violet the 
most. If we take a 
glass that reflects or 
transmits only the 
red and the blue (Fig. 
100), excluding all 
other colors, and view 
through it a lamp or 
candle flame at a dis- 
tance of 16 or 20 
feet, the blue rays 
will be more strongly 
refracted than the 
red, and come to a 
focus sooner than 
the red ones. The 
latter will be brought 
to a focus later on. 
If the eye is 
emmetropic (z. e., if 
its retina is at E in 
Plate VII), each blue 
ray crosses a red one 
at the retina; thus 
the two colors are 
mingled, and the 
flame will be seen as a diffuse violet color with a 
border of a slightly deeper hue. 

If the eye is hyperopic (HH, Plate VII), the 




Fig. yo.— Bull's Optometer. 



126 



HOW TO EXAMINE THE EYE. 




Fig. 100. Chromatic Glass. 



blue rays, converging faster than the red, meet the 
retina within the red, and thus the flame appears 
with a distinct blue center and a red border. 

If the eye is myopic (MM, Plate VII), the blue 
rays cross in front of and meet the retina as di- 
vergent outside of the red 
rays, and thus the flame 
will appear with a distinct 
red center and a purple or 
blue border. 

Landolt has beautifully 
illustrated this in his work 
on " Refraction and Accom- 
modation." 

"In Plate VII, let ABCD 
be a section of a pencil of rays given off from a red- 
blue point sufficiently distant so that these rays may 
be regarded as parallel. The focus of the blue rays 
is at b; that of the red ones at r. The eye is ad- 
justed to the distance of the luminous point when 
the circle of diffusion received upon its retina is at 
its minimum. This is the case when the sentient 
layer of the retina lies between the two foci (E, 
Plate VII). In this case the point will appear as 
a small violet circle composed of the two colors. 
If the retina be in front of this point at the focus 
of the blue rays, the eye will perceive a blue point 
surrounded by a red circle, the latter being formed 
by the periphery of the luminous cone of red rays 
which, come to a focus only after having passed 
the retina. The blue point will become a circle 
of diffusion larger in proportion as the retina is 
nearer the dioptric system, or as the focus of the 



Plate VII. 




128 HOW TO EXAMINE) THE EYE. 

in all directions ; some fall on this diaphragm ; a 
greater number, however, are cnt off, and only a 
few pass through the two openings; and if the eye 
be adapted to the flame (z. e. y if it be emmetropic), 
these two sets of rays will meet exactly on the 
retina, forming there one image of the flame (B, 
Fig. 101). 

If the eye be hyperopic (the accommodation 
put at rest), the two sets of rays will reach the 
retina before meeting, each set forming an image 
of the flame (A, Fig. 101). The greater the hyper- 
metropia, the further apart will be the images. 
These are projected outwards as crossed, and the 




Fig-. 101. 

patient sees two images of the flame. The convex 
glass which, placed behind the card, causes the 
flame to be seen singly is the measure of the 
hypermetropia. If the eye be myopic, the two sets 
of rays cross before striking the retina, reach it as 
divergent, and two images are formed (C, Fig. 101). 
These images are crossed again as they are pro- 
jected outwards, and, having twice crossed, homony* 
mous images result. To determine the amount of 
myopia, find the concave glass which, placed behind 
the diaphragm, will bring the two images into one. 
Suppose the card to be horizontal before the eye, 
and a red glass placed in front of one of the open- 




^•4: 



HOW TO EXAMINE THE EYE. 129 

ings, say the right; then, if only one flame is seen, 
the case is emmetropia. If two images of the 
flame appear, one white and the other red, the red 
to the left, it is a case of hyperopia. If the red 
appear on the right, the case is myopia. The further 
apart the images are, the greater is the ametropia. 

The test by the trial case, the first mentioned 
in this chapter, is the crucial test. This test and 
the examination by the ophthalmoscope are to be 
relied upon, while the others may be used more as 
corroborative, and in ordinary cases may be alto- 
gether dispensed with. 

Optometry by the Perimeter. This is the 
method used in determining the field of vision and 
its limitations. The field of vision is the space 
bounded by a line including all objects perceptible 
to the eye without change of fixation. For instance, 
when we look at a particular object, although the 
eye is fixed upon it, other objects at either side, 
above, or below within a certain limit are also per- 
ceived ; the further they are outside of the point of 
fixation, the more are they indistinct, for the 
further are their images from the macula lutea, 
which is the most sensitive part of the retina; 
and the sensitiveness of the retina gradually dimin- 
ishes from this part. The nose, eyebrows, and 
cheek limit the field of vision. 

At the temporal side the limit is 90°, at the 
nasal it is 50°, above it is 50°, below it is 65°. 

The perimeter (Fig. 102) is an arc, usually half a 
sphere mounted on a base and suspended on a pivot, 
so as to be rotated through all meridians. It is 
spaced into degrees from to 90 in both directions. 



130 



HOW TO EXAMINE THE EYE. 



At the foot of the instrument is attached an 
upright rest for the chin of the patient. The 
standard is about twelve inches from the center of 
the arc. The chin of the patient resting on the 
standard, the eye should be on a line with the 
center of the arc, at which point is a bright white 
Spot. The eye under- examination is to be directed 



II llfll sB 




Fig. 102. 



to the white spot, the other eye being covered. 
My custom is to turn the arc into the vertical 
position, and then pass the movable white disc along 
the arc from zero toward the circumference, until 
it passes out of view, indicating the same on the 
chart. I then rotate the arc into another merid- 



HOW TO EXAMINE THE EYE. 



131 



ian, say 15° to the left, proceeding as before, until 
I have entirely gone around to the point started 
from. The perimeter is not only useful for ascer- 
taining the Aeld of vision, but also for mapping 
any defects, such as blind spots (scotomata). The 
patient may tell you as you move the white disc 
along the arc that at certain points it disappears, 
but comes again into view as you continue to move 
it further on. For instance, it may pass out of 
view at 10°, coming in again at 20°. It may again 
disappear at 40° and reappear at 50°. Between 10° 
and 20°, and 40° and 50°, in the case supposed, there 
are blind spots. Then, by shifting the arc into an- 
other meridian, we may find that the space where 
the spot appears is shorter or longer as the case 
may be ; thus we map out the extent of the blind 
spot, or scotoma. This is of great practical value in 
certain diseases of the retina and choroid. If ex- 
aminations are made from time to time and the 
results recorded, it is easy to determine if the dis- 
ease is stationary or progressive. It is also a 
means of determining the amount of strabismus. 
(See chapter on Strabismus.) 



CHAPTER VII. 



MYOPIA. 



Myopia, brachymetropia, or near-sightedness, is 
that condition of the eye in which the refractive 
power is too great, or the antero-posterior axis of 
the eyeball is too long, the eye thus having its 
focal point for parallel rays in front of the retina; 
in other words, it is adjusted for near objects only, 
whose rays meet the eye as divergent. Therefore, 
to focus the rays of light from a distant object 
(or parallel rays) a concave glass is required to 
diverge these rays that their focus may be further 
back, or on the retina. (Fig. 103, dotted lines?) 




Fig. 103. 

The concave glass that enables the myope to 
see No. 20 of Snellen's test type at twenty feet 
would indicate the degree of myopia. However, 
many myopic eyes are non-amenable, or only par- 
tially amenable, to improvement by glasses, because 
of some other affection, as posterior staphyloma, 
disease of the vitreous, choroiditis, etc. 

The accompanying table taken from Donders 

132 



MYOPIA. 



133 



shows the increase of the length of the eyeball 
compared with the degree of myopia: 



Degree 


Amount 


of 


of 


Myopia. 


Length'ing. 


D. 


mm. 


0.0 


0.00 


0.5 


0.16 


1.0 


0.32 


1.5 


0.49 


2.0 


0.66 


2.5 


0.83 


3.0 


1.01 


3.5 


1.19 


4.0 


1.37 


4.5 


1.55 


5.0 


1.74 


5.5 


1.93 


6.0 


2.13 


6.5 


2.32 


7.0 


2.52 


7.5 


2.73 



Total length 


Degree 


of 


of 


Axis. 


Myopia. 


mm. 


D. 


22.824 Si, 


8.0 


22.98 


8.5 


23.14 


9.0 


23.31 


9.5 


23.48 


10.0 


23.65 


10.5 


23.83 


11.0 


24.01 


12.0 


24.19 


13.0 


24.37 


14.0 


24.56 


15.0 


24.75 


16.0 


24.95 


17.0 


25.14 


18.0 


25,34 


19.0 


25.55 


20.0 



Amount 

of 

Length'ing 



mm. 
2.93 
3.14 
3.35 
3.58 
3.80 
4.03 
4.26 
4.73 
5.23 
5.74 
6.28 
6.83 
7.41 
8.03 
8.65 
9.31 



Total length 

of 

Axis. 



mm. 
25.75 
25.96 
26.17 
26.40 
26.62 
26.85 
27.08 
27.55 
28.05 
28.56 
29.10 
29.65 
30.23 
30.85 
31.47 
32.13 



All myopic eyes to a certain extent are diseased 
eyes. If there is a greater degree of myopia than 
six dioptrics, perfect vision is not usually obtained 
by glasses. 

CAUSE. 

Heredity is frequently responsible for myopia. 
Myopia may increase in degree in each successive 
generation. The most frequent cause is abnormal 
increase in the length of the eyeball in its antero- 
posterior axis. This takes place after birth; and, 
though the child may be hyperopic at birth, there is 
a predisposition to myopia later in life. This ex- 
tension occurs chiefly at the posterior portion of 
the globe, and may develop into posterior staphy- 
loma (bulging backward), which is accompanied, 



134 MYOPIA. 

with rare exceptions, by thinning and atrophy of 
the choroid and sclera, and frequently with detach- 
ment of the retina. Convergence in the act of 
accommodation may induce myopia, especially in 
the young when the eye is plastic. At birth, the 
eye is usually hyperopic ; later on, it may become 
emmetropic or even myopic. 

These eyes should always be examined with 
the ophthalmoscope in order to ascertain whether 
the condition of the optic nerve and retina be nor- 
mal, or whether they are hypersemic and congested; 
and they should also be examined for posterior 
staphyloma. 

We have seen from the anatomical structures 
of the ciliary region that the ciliary muscle and 
ciliary processes, as well as the ora serrata, the liga- 
mentum pectinatum iridis, and the choroid are all 
intimately connected (Plate IV). In the exercise 
of the power of accommodation there is more or less 
strain on the choroid, and, in fact, upon the whole 
uveal tract; and if this power be overtaxed, as is 
frequently the case with school-children and those 
who are compelled to use their eyes continuously 
for near objects, affections of this part of the eye, 
such as choroiditis and cyclitis, are liable to follow. 
It is a well-known fact that choroiditis is a frequent 
forerunner of myopia with posterior staphyloma 
or sclero-choroiditis posticus. The eye continu- 
ously employed for near objects for too long a 
time is liable to spasm of accommodation. We 
know that the eye when adjusted for near objects 
is temporarily myopic; that is, it is adjusted for 
divergent rays. In spasm of accommodation the 



MYOPIA. 135 

eye fails to relax and readjust itself for distant 
objects and therefore remains permanently fixed for 
near objects; or, in other words, is myopic. Con- 
tinued tension, then, of the accommodation for 
near objects is a cause of myopia. This accounts 
for its greater frequency among the higher and lit- 
erary classes than among the illiterate. 

The production and increase of myopia by con- 
tinuous use of the eyes at near objects, as reading, 
writing, sewing, engraving, watchmaking, etc., ap- 
pear to find their explanation chiefly in the fact 
that the inner tunics of the eyeball become con- 
gested, and finally inflammation and giving way of 
these membranes ensue. The near approach of the 
object necessitates a strong convergence of the optic 
axes; "this gives rise to a strain of the muscles and 
tunics of the eye. The stooping position generally 
indulged in during such employment will also 
produce congestion by inviting an accumulation of 
blood to the inner tunics, which may finally result 
in inflammation. This congestion or augmentation 
in pressure, if long continued, necessarily leads 
to an extension of the tunics at the posterior pole 
and so induces posterior staphyloma. 

A clouded cornea or an opaque lens may cause 
myopia from the patient's bringing the objects 
nearer to the eye in order to obtain larger and 
more distinct retinal images. The degree of myopia 
is often increased during childhood by long-con- 
tinued study; also by insufficient illumination and 
a faulty construction of the tables or, desks at 
which the pupils read or write. 

Referring to the report gathered from the ex- 



136 MYOPIA. 

amination of 2040 school children (see appendix), 
we find that in one school the largest per cent of 
defective eyes was fonnd in the lower grades, where 
the first and second year pupils .(for want of ade- 
quate accommodation) were crowded into a room 
calculated for older pupils, and hence the distance 
between the desk and the seat was too great, as 
well as that from the seat to the floor, compelling 
the little pupil to hang, as it were, upon the desk, 
nis feet not touching the floor. This position, of 
necessity, brought his face too near the book or 
slate, and hence taxed the power of accommodation 
of the eye to a great degree, which resulted in 
spasm of accommodation — a forerunner of myopia. 

An insufficient illumination necessitates a close 
approximation of the object, which gives rise to a 
strain of the accommodation and congestion of the 
eyes — another cause of spasm of the ciliary muscle. 

Myopia is found in a larger per cent among 
the German people than in those of other nation- 
alities. The style of type probably has something 
to do with this, as it requires a greater effort to see 
the German text than the Latin text. It is still 
a query whether tobacco may be regarded as an 
etiological factor of myopia. Small print, long 
lines, or a narrow space between the lines lie in 
the same category of criminal factors of myopia. 
Germans are now using the Latin text, and myopia 
is gradually diminishing among them. 

The myope is more reticent, is less inclined 
to engage in out-of-door sports, and occupies his 
mind in literary pursuits. From the very fact that 
he is shut out largely from the subtle beauties of 



MYOPIA. 137 

nature and the ordinary out-of-door sports, he be- 
takes himself to his friends — his books. His eyes, 
therefore, are more constantly subjected to the strain 
of convergence and accommodation in looking at 
small and near objects. 

It was formerly supposed that increased con- 
vexity of the cornea was the cause of myopia, but 
this is erroneous, for Donders has found that the 
cornea is, as a rule, less convex in myopic persons 
than in the emmetropic. Increase of the curva- 
ture of the cornea (as in conical cornea) may, how- 
ever, provoke or be concurrent with myopia. 

SYMPTOMS. 

Distant objects do not present a clear and well- 
defined outline, but appear irregular, enlarged, and 
surrounded by a halo. In order, therefore, to im- 
prove the vision for distant objects, persons often 
acquire the habit of nipping the lids together. 
This, first, narrows the opening between the lids 
(palpebral aperture), cuts off some of the periph- 
eral rays of light, and diminishes the circles of 
diffusion on the retina; thus, the object gains in 
distinctness of outline. 

Second, a certain amount of pressure is exer- 
cised upon the eyeball, the cornea rendered some- 
what flatter, and the refraction thus slightly di- 
minished. 

The myopic eye, as a rule, is a large, full eye 
and is prominent. Compared with the hyperopic 
eye, the cornea is larger. The myopic eye is clearer 
and has not so much ciliary hyperaemia as is often 
seen in the hyperopic eye, due to the fact that the 



1 38 MYOPIA. 

latter is always exercising its accommodation, thus 
giving rise to this ciliary congestion. If the lids 
are separated, it will be seen that the curvature of 
the equator of the myopic eye is less abrupt than 
that of the hyperopic eye. 

PATHOLOGY. 

In considering the pathology of myopia we 
might mention, besides the affections of the cho- 
roid and of the retina with posterior staphyloma, 
metamorphopsia y or derangement of the cones in the 
macula, which causes an irregular or curved ap- 
pearance, straight lines or pins appearing wavy or 
crooked; and widening or crowding together of 
the rods, with other displacements, giving the ef- 
fect of magnifying, reducing, or warping the image 
of the object. Letters are uneven and some stand 
higher than their neighbors. Sometimes the pa- 
tient will speak of a certain part of the object 
looked at as on a higher plane than the other 
parts, or of the object having a wavy appearance. 
I remember especially one patient who complained 
of these symptoms, who had received a blow upon 
the eye without reducing the vision very much; 
she was greatly disturbed by this metamorphopsia. 
This derangement is due to exudation or infiltra- 
tion of matter into the retina, disarranging the 
rods and cones. 

Megalopsia. Sometimes, objects appear larger 
than they really are. This condition is called 
megalopsia. It is due to the crowding of the ele- 
ments of the retina together, the image embracing 
more of the rods and cones than normally. 

Micropsia. This is a condition where the ob- 



MYOPIA. 139 

ject appears smaller than it really is, and is dne 
to a spreading or separation of the rods and cones, 
the image embracing less of them than normally. 

DIAGNOSIS. 

The diagnosis is generally easy. Distant ob- 
jects cannot be clearly distinguished and a suit- 
able concave glass may render them distinct. How- 
ever, a person may hold small objects very close 
to the eye, or not be able to see well at a distance, 
and yet not be myopic, but hyperopic, and require 
a convex glass instead of concave. 

Myopia may be confounded with amblyopia — 
weak sight. Weak-sighted persons bring small 
objects very close to the eye in order to gain mag- 
nified images. Concave glasses do not enable them 
to see better or further off; on the contrary, they 
see worse with them. If a concave glass of the 
strength of two or more dioptres improves vision, 
myopia exists; but improvement with a weaker 
concave glass does not necessarily signify myopia, 
as a hyperopic eye with spasm is often improved 
by a weak concave glass. In contradistinction to 
myopia, a convex glass, no matter how weak, 
which improves the sight for distant objects, signi- 
fies hypermetropia. In examining the eye the test 
may be objective or subjective. (For the various 
tests for myopia, see Chapter VI.) 

PROGNOSIS. 

If the myopia be stationary and there be 
no staphyloma, especially in the young, there 
is virtually nothing to be feared; but such is 
not the case in the adult or in persons further 



140 MYOPIA. 

advanced in life, especially if the myopia be increas- 
ing. There is great danger of the staphyloma pro- 
gressing to final destruction of vision. Myopia ex- 
ceeding 6 D. should be looked upon as serious ; it is 
called malignant myopia. That of less than 3 D. 
is called simple myopia, and in the adult is usually 
stationary. That between 3 D. and 6 D. is medium 
myopia, and is liable to progress. In a high de- 
gree, the younger the subject the greater is the 
danger, as the disease is very liable to increase. 
Later on in life, extensive staphyloma and disease 
of the choroid and of other parts of the fundus are 
liable to follow. If there be a large crescent with 
perhaps pigmentary patches and the vision be less 
than 6 D., the prognosis is grave. 

In such myopic people the eye should be care- 
fully examined by the oculist; the field of vision 
and any existing scotomata should be carefully 
mapped out by the perimeter (Fig. 102, page 130), 
and the vision taken; all of which should be made 
a matter of record. These examinations should be 
made from time to time to see whether there is any 
increase in the myopia, staphyloma, or scotomata. 
If so, the progress may be checked or arrested by 
changing the habits and occupation of the patient. 
Out-of-door life should be encouraged, and the 
employment of the eyes for near and small objects 
discouraged. 

Now, in regard to the myope becoming in proc- 
ess of time an emmetrope, let me say that while 
static refraction diminishes after a certain age, ren- 
dering an emmetrope a hyperope, it is only when 



MYOPIA. 141 

the degree of myopia is very slight that this eye 
becomes emmetropic. 

This diminution of static refraction commences 
at the age of fifty, and at eighty amounts to 2.5 D., 
so only the myope of not more than 2.5 D. can be- 
come emmetropic even at the age of eighty. A 
myope with less than 1.5 D. may become hyperopic. 
Occasionally, people with an excessive degree of 
myopia, scarcely able to see a foot away, become 
emmetropic or even hyperopic. But this is only 
for a very short time, and is always a sad premoni- 
tion ; for while a new world with its minutiae and 
glow is for a little while opened to them, everlast- 
ing darkness is soon to follow. By the detach- 
ment of the retina and its falling forward, the eye 
temporarily becomes perhaps emmetropic ; but soon 
the retina, thus detached, loses its vitality, and 
blindness is the consequence. 

SEQUEL. 

In a high degree of myopia, especially in the 
young, sooner or later complications arise which 
are due directly to the condition of the myopic 
eye. Posterior staphyloma is one of the most seri- 
ous and most frequent sequelae of myopia. The 
extension of the eyeball backward causes a thin- 
ning of the different tunics, and sooner or later 
the retina and choroid give way, and a crescent 
varying in size and extent is to be seen at the 
disc. Frequently, the whole retina is detached, re 
suiting in total blindness. Retinal haemorrhage and 
haemorrhage between the retina and choroid are 
often associated with or dependent upon myopia. 



142 MYOPIA. 

The following case illustrates one of the many 
dire consequences of this anomaly: 

Case. The patient was a man, a farmer, aged 
thirty years, who became suddenly blind after load- 
ing a car with baled hay on a hot June day. After 
he entered his wagon to return home, he found 
himself suddenly blind of both eyes. Examina- 
tion revealed haemorrhage of the macula with a 
detachment of the retina, and although the haemor- 
rhage was absorbed and the retina reattached itself 
for a time, other haemorrhages followed, and in the 
course of a few years he became totally blind. 
This patient had only a moderately high degree 
of myopia. This is one of the many sad cases 
that come under our observation. 

A high degree of myopia existing in childhood 
is almost sure in later life to end in serious ini*- 
pairment if not in total destruction of vision. 
Many highly myopic eyes become sooner or later 
cataractous, but the cataract develops very slowly. 
Frequently the vitreous becomes diseased — partially 
fluid — and not infrequently is there luxation of 
the lens. The vitreous loses its consistency and 
shrinks, and thus favors detachment of the retina 
and intraocular haemorrhage. 

\- The myopic eye is far more prone to atrophy 
of the optic nerve than the emmetropic or even 
the hyperopic eye. The myopic person is almost 
invariably annoyed by what is termed muscce voli- 
tantes, and what would be physiological in an 
emmetropic eye is frequently pathological in the 
myopic eye; the " floaters' ' of the vitreous become 
more numerous and opaque, thus obscuring vision. 



MYOPIA. 143 

The myopic eye is more frequently attacked 
"by hyalitis and choroiditis than the emmetropic; 
hence, the importance of great care not to overtax 
or abuse this eye. It should be carefully watched, 
and any complications arising should receive timely 
and skillful treatment. 

TREATMENT, 

Prophylactic Treatment. Myopia, which 
•reduces the capacity for enjoyment of the beauti- 
ful outer world so greatly, can with knowledge 
and judicious care be greatly controlled in its de- 
velopment. No child is born myopic. The trou- 
ble usually develops in early life, while yet the 
eye is comparatively plastic. Close work, viewing 
small objects for a continued length of time or 
with great frequency, is liable to strain the power 
of accommodation, producing hypersemia and con- 
gestion of the fundus. This may induce a yield- 
ing of the tissues, causing prolongation or staphy- 
loma of the globe. 

In view of this, thoughtful people will readily 
see the importance of giving the young child ob- 
jects of considerable size, of easy sight, for his 
playthings. Small ones, necessitating an effort of 
accommodation to see them, should by no means 
be given, neither should the games be such as to 
require short vision. Give the child wide range of 
out-of-door plays, requiring only distant vision, or 
let the objects be sufficiently large that they may 
be easily seen without the effort of accommodation. 

When the child is in school he should not be 
allowed to use his eyes for near work long at any 
one time. The habit of some teachers, conscien- 



144 MYOPIA. 

tiously ignorant though, they may be, of requiring 
pupils to keep their eyes fixed upon their books 
through the study hours, under pain of commit- 
ting a misdemeanor if they once take them off, is 
pernicious in the extreme. Treat any other mem- 
ber of the body thus — the arm, for instance — hold 
it out in any one position for a few minutes, a 
much less time than a study hour, and you will 
soon realize what it means to violate the great law 
of nature. Such constant strain of the accommo- 
dation will, if persisted in, almost inevitably result 
in myopia. 

That the eye may perfectly develop, it should 
have frequent change of its range of vision — near 
to distant, distant to near. Frequent interruption 
of any kind of work is essential to symmetrical 
development and the maintenance of a healthy con- 
dition of the visual organ; especially is this true 
with the young. 

A child predisposed to myopia should be kept 
out of the school-room until he is at least ten 
years of age. Open-air sports should be encour- 
aged, and the child should be occupied with large 
and distant objects rather than with small and near 
ones. Gymnastic exercises, and, in fact; any and 
all means of development of the general system, 
should be prescribed. The deleterious effects of all 
stimulants, and especially of narcotics, should be 
thoroughly impressed upon the mind of the youth. 

Those predisposed to myopia should not bt 
allowed to use the eyes for near objects for any 
great length of time. Two or three hours a day 
should be the maximum for study. 



MYOPIA. 145 

Print is another matter that must be carefully 
looked to. Defective, blurred print should never 
be read — very fine print should also be banished, 
from school-books especially. 

The Latin type is by far the best. The height 
of letters should not be less than 1.5 mm., and the 
distance between each word should not be less 
than 5 mm. The interlinear distance should be at 
least 3 mm., and the length of a line should not ex- 
ceed 100 mm. This subject of type, character, size, 
etc., is of vast importance. The letters should be 
clear, sharp, and of good size. German type should 
not be employed in text-books. Pica or great 
primer is the size that seems best in ordinary 
use for text-books. We Americans realize the vast 
difference between our Latin type printed books 
and that which the Germans until recently were 
obliged to read in all their literature. 

I doubt not that this German type is twin sister 
to the studious habits of the German nation in caus- 
ing its enormous percentage of myopes. 

Children under ten years should not be required 
to study more than two and one-half to three 
hours a day; those over ten and under sixteen, 
three and one-half or four hours; and those over 
sixteen may be allowed to have longer time, but 
not more than six hours a day. No child should 
enter the school under seven years of age. Young 
pupils should be allowed to rest their eyes occa- 
sionally by glancing from their books to more 
distant objects, thereby relaxing the power of 
accommodation. 

Myopia is never congenital, although it may 



146 MYOPIA. 

appear soon after birth ; it may, however, be 
hereditary. It is frequently caused by overuse or 
abuse by holding the book or work too near the 
eyes. Long-continued use of the eyes in reading 
small print, the stooping posture, bad or insuffi- 
cient light, or a glare of light, any one or all of 
these combined have -a tendency to cause myopia. 

In bookkeeping, where there is a necessity for 
fixing the vision intently, as in casting up long 
rows of figures, the power of accommodation is on 
a stretch for a long time. This is especially pro- 
vocative of spasm of accommodation, which may 
finally lead to myopia. 

The light should be ample; it should not be 
reflected light, and should never come from in 
front ; but from the side, behind, or above. Prefer- 
ably it should come from the side, as light coming 
from above or behind the pupil is liable to cast a 
shadow upon the book or work. Light in the 
school-room should come mainly from the north, 
although a due amount of sunlight should be ad- 
mitted to the room. Daylight is the best light) 
and all work of the student by artificial light 
should be discouraged. If, however, artificial light 
must be employed, the electric incandescent seems 
the best, as it is perhaps the nearest approach to 
sunlight that we have. The electric arc light is 
an unsteady light, varying in its brilliancy from 
dazzling to an insufficient illumination, and is very 
trying to the eyes. The incandescent light is also 
dazzling, and should be employed with a shade. 
The oil lamp with a Rochester burner gives a 



MYOPIA. 147 

steady, clear light, and in some respects is even 
to be preferred to gas or electric light. 

The space area for admitting daylight to the 
school-room should equal at least one-fifth of the 
area of the floor of the room. The light reflected 
from white walls is very severe upon the eye. Walls 
should be tinted gray or light blue. A child with 
progressive myopia, however slight, should be pro- 
hibited from reading or using his eyes for near 
vision; especially should this be emphasized if 
artificial light is used. 

To go further back in the prevention of myopia, 
as well as other evils, we might profit by the wise 
saying laid down in the laws of Moses, that the 
evils and indiscretions of the parent are visited 
upon the progeny, even to the third and fourth 
generation. It is a well-known fact that consan- 
guinity is responsible for not only anomalies of re- 
fraction, but also for diseases of the eye, and of the 
ear, with total loss of sight and hearing. We have 
examples every day betraying the sad consequences 
of the marriage of people of the same blood or of 
people with these anomalies. 

The excessive use of tobacco on the part of the 
parents, as well as by the student himself, is an- 
other well-known cause of affections of the eye. 

Of the influence of more favorable appointments 
of the school-room and a lessened number of hours 
of work therein upon myopia, I would cite in evi- 
dence statistics given by Cohen, who found the 
percentage of myopia 40. Later investigators, Von 
Reuse, Seggel, and Reich, all found an increase of 
the percentage of myopia keeping pace with the 



148 MYOPIA. 

length of time in the schools. Erisman found 
among scholars occupied 

2 hours per day 17% 

3 hours per day 29% 

6 hours per day 40% 

The results of my own examination of 2040 
pupils in Kansas and Missouri show only 5 per 
cent of- myopia. Had I added the cases of spasm 
of accommodation which simulates myopia, the per- 
centage would have been much greater. Many of 
the buildings occupied by these pupils are of late 
construction, and have generally excellent appoint- 
ments in regard to seats and hygienic conditions. 
Where these appointments were most faulty I 
found the greatest percentage of trouble. 

TREATMENT BY GLASSES. 
Since myopia cannot be cured, but only cor- 
rected, the principal treatment of myopia is glasses 
for the correction of the anomaly. To ascertain 
the proper glass, a definite plan must be followed 
out: first, ascertain the amount of vision. Place 
the patient at twenty feet from Snellen's test type 
and test each eye separately. Adjust the trial 
frame (Fig. 74, page 86) to the patient's face. Test 
the right eye first, covering the left with an opaque 
disc. Note how far down the card the person can 
read the letters. If he can see only number 80 at 
twenty feet, his vision is but twenty-eightieths. If 
he is not able to see the largest letter at 20 feet, 
have him approach the card, asking him to stop as 
soon as the largest letter comes into view. Note the 
distance from which he is able to see this letter. If 
he has to come within 5 feet, his vision is Eve two- 
hundredths, since the largest letter should be seen 



MYOPIA. 



149 



at 200 feet. Now have him return to his former 
place at 20 feet from the card, and see what con- 
cave glass will improve his vision. Begin with a 
weak glass, say 1 D. or 2 D., and continue from this 
to a stronger until the glass is found that gives 
him the greatest amount of vision. Prescribe 
always the weakest concave glass that will give 
the greatest amount of vision. It is always better 
to under-correct than to over-correct myopia. If 
too strong a glass be used, it necessitates the 
exercise of the power of accommodation, which, 
in the myopic eye, is, from its construction, fee- 
ble. If the power of accommodation is brought 
into requisition by too strong a glass, further 
complications are liable to be provoked, such as 
choroiditis, congestion of the retina, and increase 
of staphyloma. If the myopia be of a high de- 
gree, it is advisable to prescribe two pairs of 
glasses, one for distant and the other for near ob- 
jects, a stronger glass for the former and a weaker 
one for the latter. 

We have already seen that the myopic eye is 
adjusted for near objects; for rays of light com- 
ing from a near point strike the eye as divergent, 
and their focus would be at a greater distance 
back of the principal focus of the eye than that of 
parallel rays. The myopic eye, having an increased 
antero-posterior axis, or a high degree of refrac- 
tion, is already adjusted for divergent rays or those 
from a near point, and if the object be approxi- 
mated to the eye, the focus may fall upon the retina 
without any effort of accommodation, or the aid of 
a glass, unless it be a very high degree of myopia. 



150 MYOPIA. 

If so, a glass sufficiently strong should be used to 
increase the divergence of the rays as they enter 
the eye so that they may have their focus on the 
retina; it is only in these cases of high degree of 
myopia that a glass is required for near objects. It 
is frequently found, however, that people with a con- 
siderable amount of myopia are able to use the same 



Fig. 104. 

glass for near as for distant objects; the glass ren- 
ders them emmetropic, and so they use the same 
for near objects by bringing into requisition their 
power of accommodation, as does the emmetrope. 
Usually, in low forms of myopia no glass is required 
for near objects. 



MYOPIA. 151 

In the adjustment of spectacles, care should be 
taken that the frames properly and accurately fit 
the face and that the glasses be accurately centered. 
The distance between the two pupillary centers 
should be taken, and also the distance from the 
median line of the nose to the center of each pupil. 
For this purpose, a pupillolneter (Fig. 104) may be 
used. It is the custom of most oculists and opti- 
cians to take merely the pupillary distance, measur- 
ing from the center of one pupil to the center of the 
other. This measurement would suffice in the ma- 
jority of cases, yet there are exceptions where the 
nose is not in the median line or the eyes are not 
symmetrically placed, the distance from the center 
of the pupil of one eye to the median line of the 
nose being greater than that of the other.* This 
should be taken into consideration and each glass 
accurately centered. The glasses should be on a 
plane parallel with that of the iris, tilted neither 
upward nor downward, inward nor outward. If 
the glasses are not centered and the person looks 
through the edge, the glass acts as a prism, and 
of necessity taxes certain muscles; or if the glasses 
be tilted, they act as cylinders and create an astig- 
matic effect. 

These foregoing facts may be taken advantage 
of, however, in cases where there is some hetero- 
phoria or astigmatism. If it be a case of exophoria 

*In case of such an asymmetry, the distance from the median line of the 
nose to the center of the pupil of each eye should be taken separately. If the 
pupillometer is used, adjust the indicator to the center of the pupil of one eve, 
and half the amount registered indicates the distance from the median line" of 
the nose to the pupillary center. The other eye should be examined in the same 
manner. 



152 MYOPIA. 

with myopia, the concave glass should be decen- 
tered outward, that the base of the prism be 
toward the internal rectus, or muscle to be relieved; 
also in esophoria with hyperopia, the convex glass 
should be decentered outward, that the base of the 
prism be toward the external rectus, or muscle to 
be relieved. Hyperphoria and cataphoria may be 
relieved by decentering the concave glass upward 
or downward, as the case may be. A slight amount 
of astigmatism can be corrected by tilting the 
glasses; but it is only in rare cases that this is 
to be recommended. Care should be taken to select 
frames of strong and yet as light material as pos- 
sible. For myopic persons, from obvious reasons, 
the hook bows are preferable to the straight, or 
to the nose glasses. The myopic person should 
be cautioned against bringing the object too near 
the eye, and also against, the stooping posture. He 
should be instructed to sit erect while reading or 
working, and keep the book or work as far from 
the eyes as convenient. Spasm of accommodation 
simulates myopia, and a mydriatic should be used 
in all slight forms of myopia or suspected myopia 
before prescribing glasses. 

Many people object to the wearing of spectacles; 
especialry does the mother frequently object to 
putting glasses on her child, fearing that, once on, 
they will always have to be worn; others dislike 
to acknowledge any defect or imperfection of their 
child's eyes. Though we may sympathize with 
the child who is compelled to resort to glasses, yet 
if the eye is imperfect as to its refraction, these 
imperfections can not be cured by medicaments; 



■ 



MYOPIA. 1 53 

but they should be corrected and the eye thus 
strengthened by the use of proper spectacles adjusted, 
and so rendered not only stronger, but largely 
indemnified against an increase of the myopia and 
many of the complications likely to arise if it is 
not so fortified. If care and attention be given to 
this subject by the present and immediately suc- 
ceeding generations, this important organ of vision 
may be so improved, with the body in general, in 
its anatomical and physiological condition, that 
future generations will inherit a more perfect organ 
— one which, to a certain extent, will be immuned 
against anomalies and their sequelae. 

It is thought that civilization and a high degree 
of culture are responsible for myopia, and statis- 
tics show that myopia is more frequently found 
in literary persons than in the illiterate, and the 
reverse is true of hyperopia. This being a fact, 
there must be some fault in our system of educa- 
tion, mode of living, or habits of life. This is a 
subject that should interest all, and it is interest- 
ing thinking people, and especially educators, through- 
out the land. Much attention is now being given to 
the condition of the school-rooms as to light, ven- 
tilation, arrangement of seats and desks, and the 
length of the study hours. 

If myopes are allowed to select their own glasses, 
they are apt to choose too strong ones. If there is 
much asthenopia, a blue glass may be prescribed 
to temper the light. Occasionally, where there is 
very much asthenopia, tenotomy has to be made, 
but frequently a slight amount of heterophoria can 
be overcome by decentering the glass. The myope 



154 MYOPIA. 

with considerable degree of anomaly is predisposed 
to detachment and haemorrhage of the retina, 
particularly at the macula. Such a person should 
avoid violent exercise or heavy work that requires 
much lifting or straining. 

Myopia is much affected by the nervous condi- 
tion of the patient, and all excessive indulgence 
on the part of the parent or progenitor in alco- 
holic stimulants or in tobacco is liable to find its 
dire consequences in the impaired vision of the 
child. 

LUXATION FOR MYOPIA. 

Should we luxate or extract the lens for the 
correction of excessive myopia? 

This treatment has been suggested by Dr. 
Priestley Smith. 

The extraction of the lens has the same effect 
as placing a concave glass of 11 D. before the eye. 
In case of a higher degree of myopia than 11 D., 
after the lens is extracted, a concave glass of the 
strength corresponding to the difference between 
the myopia and 11 D. would have to be used. 

In a lower degree than 11 D., with the lens 
extracted, a convex glass would have to be used 
corresponding in strength to the difference between 
11 D. and the amount of myopia. 

In these high degrees of myopia there is usu- 
ally some disease at the fundus, and it has been my 
experience that correction of* the myopia by the 
extraction of the lens does not always gain the 
improvement one might expect. 



CHAPTER VIII. 



HYPKRMKTROPIA. 



The word hypermetropic!,, or hyperopia, comes 
from the Greek and signifies that the focns of the 
eye is beyond the measnre — retina — or, in other 
words, it is that condition of the eye whose antero- 
posterior axis is either too short or its refraction 
is too low, in consequence of which parallel rays 
of light as they pass through the dioptric media 
are not focused upon the retina, without an effort 
of accommodation, but meet it before they come 
to a focus, and thus form circles of diffusion (BB, 
Fig. 105), which give a blurred and indistinct image. 
To bring these rays of light to a focus on the 
retina, (dotted lines, Fig. 105), that a sharp image 
may be gained, a converging lens is necessary. 




Fig. 105. 

The hyperopic eye is an undeveloped eye, be- 
ing smaller than the emmetropic in all its dimen- 
sions. As a rule, there is a deficiency of the rods 
a"nd cones of the retina as well as of the optic 
nerve fibres. The disc is frequently of an oval 
form, simulating astigmatism. The vision, save in 
rare exceptions, is not equal to that of the emme- 
tropic eye. The nodal point being nearer the retina 
than in the emmetropic eye, all images are cor- 
respondingly less in size. 

155 



156 



HYPERMETROPIA. 



The axis of the eyeball in the hyperopic eye is 
shorter than in the emmetropic; and the greater 
the amount of hypermetropia, the shorter is the 
optic axis, and vice versa. 

The accompanying table from Donders shows 
the amount of shortening of the axis of the eye- 
ball compared with the degree of hypermetropia: 



Degree 


Amount 


Total Length 


Degree 


Amount 


Total Length 


of 


of 


of 


of 


of 


of 


Hyperopia 


Shortening. 


Axis. 


Hyperopia 


Shortening. 


Axis. 


D. 


mm. 


mm. 


D. 


mm. 


mm. 


0.0 


0.00 


22.824£d 


8.0 


2.28 


20.54 


0.5 


0-16 


22.67 


8.5 


2.41 


20.41 


1.0 


0-31 


22.51 


9.0 


2.53 


20.29 


1.5 


0-47 


22.35 


9.5 


2.66 


20.16 


2.0 


0*62 


22.20 


10.0 


2-78 ... 


20.04 


2.5 


0-77 


22.05 


10.5 


2-90 


19.92 


3.0 


• 0.92 


21.90 


11.0 


3.02 


19.80 


3.5 


1.06 


21.76 


12.0 


3.25 


19.57 


4.0 


1.21 


21.61 


13.0 


3.47 


19.35 


4.5 


1.35 


21.47 


14.0 


3.69 


19.13 


5.0 


1.50 


21.32 


15.0 


3.91 


18.91 


5.5 


1.62 


21.20 


16.0 


4.11 


18.71 


6-0 


1.76 


21.06 


17.0 


4.32 


18.50 


6.5 


1.90 


20.92 


18.0 


4.52 


18.30 


7.0 


2.03 


20.80 


19.0 


4.71 


18.11 


•7.5 


2.16- 


20.66 


20.0 


4.90 


17.92 



The common term with, the laity for hyperopia 
is " far-sightedness," a contradistinction from near- 
sightedness, and the idea is prevalent that the 
nyperope can see objects at a distance better than 
an emmetrope — a normal-sighted person. This is a 
mistake; the hyperopic eye is an undeveloped eye, 
with, sight not up to the normal standard of dis- 
tinctness either for near or distant objects. 

All babies are born hyperopic ; the eye should 
afterward develop into the emmetropic eye, and may 



HYPERMETROPIA. 



157 



become myopic; and when once any considerable 
degree of myopia is attained, the eye never again 
becomes liyperopic except artificially by the re- 
moval of the lens, or by the detachment of the 
retina. 

Myopia nsnally increases by nse of the eyes, 
never diminishes except in later years. Hyperopia 
rarely, if ever, increases, bnt frequently dimin- 
ishes. Myopia tends to increase, while the tendency 
of hyperopia is to decrease. 

Static refraction increases in childhood, but 
after the period of adolescence it remains station- 
ary. IvanofF shows that the hyperopic eye has a 
larger ciliary muscle than the myopic or the 
emmetropic (Figs. 68, 69, and 70, pp. 78 and 79); 
the circular fibres, especially, are highly developed, 
while the myopic eye has few or no circular fibres. 
It has been demonstrated that the macula lutea is 
further to the temporal side in the hyperopic eye 
than in the emmetropic eye, and hence the dis- 
tance between the disc and the macula is greater, 
and therefore the angles alpha and gamma are 
large; so the hyperopic eye, of necessity, has to 
exert a greater amount of convergence when look- 
ing at near objects than the emmetropic or the 
myopic eye. 

The hyperopic eye of a moderate degree with 
good power of accommodation may have the nor- 
mal amount of vision — that is, be able to see -f §-, and 
thus pass for an emmetropic eye; but, unlike the 
emmetropic, which is adjusted for parallel rays or 
those coming from distant objects, requiring no 



158 HYPERMETROPIA. ' 

effort of accommodation, the hyperopic eye to gain 
!§- has to exert its power of accommodation. If 
the hyperopia is of a low degree, the person may 
snffer no inconvenience from this constant tax, 
especially if he has to deal mostly with distant 
objects; bnt we can readily see that if the eye has 
to exert its power of accommodation for parallel 
rays, this exertion mnst be still greater for diver- 
gent rays, or those coming from near objects; and 
the greater the degree of hypermetropia, the greater 
is the strain on the ciliary mnscle. This is made 
manifest in what is known as muscular asthenopia, 
ciliary neuralgia, or migraine. 

The hyperopic eye varies in its amount from 
a fraction of a dioptre to ten or fourteen dioptres; 
hyperopia of six D., however, is considered a high 
degree. An eye of 50 D. , as spoken of in Dr. 
Noyes' text-book, page 88, would be such a small 
eye that it would come under the head of mi- 
crophthalmias (ophthalmidium) rather than of 
hypermetropia, and would be almost sure to be 
defective in other respects. 

In a hyperope of more than four D., the vis- 
ion is always less than normal. Hypermetropes 
with less than 3.50 D., with good accommodation, 
as a rule, have |J, or normal vision. Frequently 
convex glasses do not improve their vision, although 
the ophthalmoscope will show an amount varying 
from one to four or five D. Many of these peo- 
ple will accept a weak convex glass, say from 0.50 
D. to 1 D , which will bring their vision up to -§§; 
some requiring not more than a fraction of a diop- 
tre to gain normal vision, but will yet accept a 



HYPERMETKOPIA. 159 

stronger glass, as 1 D. or 2 D., or even more. Usu- 
ally, these hyperopes under atropia require a much 
stronger glass, — for instance, 3 D. or 4 D., — and if 
the power of accommodation is fully set aside, the 
glass that will give them the greatest amount of 
vision indicates the amount of their hypermetropia. 

The strongest glass that they require without 
the use of a mydriatic indicates the manifest hyper- 
metropia. The difference between this glass and 
the one required after the power of accommoda- 
tion is fully set aside shows the amount of latent 
hypermetropia . 

The manifest is .usually apparent without a 
mydriatic; the latent is revealed by it. As a rule, 
the latent is of greater amount than the manifest. 
These two constitute the dynamic refraction. The 
manifest is usually corrected for a time, at least, 
by the power of accommodation (dynamic refrac- 
tion); but if the dynamic is much exercised, as for 
reading, etc., the eye becomes tired and a train of 
asthenopic symptoms appears, demanding relief. 

SYMPTOMS. 
Subjective Symptoms. The patient complains of. 
pain in the region of the eye, sometimes in the 
center or back part of the eyeball, but more fre- 
quently through the temple and over the brow. 
The pain is occasionally referred to the back of 
the head, and may be accompanied by nausea and 
vomiting. The patient will often speak of a 
frontal headache, which by the French has been 
called migraine. The neuralgic headache and the 
intense pain through the temple and over the 
brow, streaking down the nose and cheek, are usu- 



16U HYPERMETROPIC. 

ally to be attributed to Hyperopia. The patient 
will often speak of being unable to use his eyes 
for a considerable length of time without weari- 
ness, drowsiness, drooping of the lids, and inclina- 
tion to close them; and if he persists in his work 
for a great length of time, the pain becomes 
severe, the page blurs, letters are indistinct and 
dance upon the page, the lines skip over one an- 
other, and the reading has to be discontinued; but 
if he rests his eyes for a little time, batting his 
lids or closing them, thus relaxing his accommo- 
dation, he is able to resume the work; if he per- 
sists, however, the same symptoms repeat them- 
selves, and finally he is obliged to desist altogether. 
The above symptoms constitute the condition 
known as asthenopia. 

Objective Symptoms. The hyperopic eye, as 
already said, is an undeveloped eye; it is usually 
deeply set in the orbit; however, in some rare 
cases the hyperopia is due to a low refractive 
power, and not to the length of the eyeball, and 
the eye is fully up to the standard in size in all 
dimensions. As a rule, the hyperopic eye is not 
so clear and bright in appearance as the emme- 
tropic eye, being slightly red, as there is more or 
less hyperemia, especially in the ciliary region; 
this hyperemia is probably due to the constant 
effort of accommodation. 

It is sometimes found that a hyperope who can 
see the last letters on the card at twenty feet, or 
whose vision is apparently normal, will accept a 
convex glass, the glass sharpening his vision and 
relieving the eye. This always indicates hyper- 



HYPERMKTROPIA. 161 

opia. Sometimes the hyperope with vision of •§£ 
will accept a glass as strong as 3 or 4 D., which 
shows a high degree of facultative accommodation. 
As a rule, in the hyperopic eye the pupil is smaller 
and the person seeks strong light. If the hyper- 
ope does not wear glasses in early life, he is com- 
pelled to put them on for reading sooner than 
the emmetrope; in other words, he becomes pres- 
byopic sooner than the emmetrope. A hyperopic 
person may worry on and continue to use his eyes 
for years without the aid of glasses, but in case 
of ill health the power of accommodation gives 
way and the anomaly becomes suddenly manifest. 



CAUSE. 

Hypermetropia is a congenital defect, due to a 
shortened visual axis, or deficiency in the lens. 
In old age it may be due to a flattened condition 
of the lens, and in glaucoma to a flattened condi- 
tion of the cornea due to extension of the globe. 

That hyperopia is hereditary, there is no doubt. 
This can be demonstrated daily in our practice. 

In women any uterine trouble may provoke 
asthenopic symptoms. Some women during the 
catamenia or during pregnancy have more or less 
asthenopia. Endometritis is frequently provoca- 
tive of ciliary neuralgia. 

The conformation of the orbit has much to do 
with the development of the eye, as to its being 
emmetropic, myopic, or hyperopic; especially is 
this tru? in many cases of anisometropia. Ametro- 
pia is frequently associated with asymmetry of the 
cranium and face. 



162 HYPERMETROPIC. 

The contour and shallowness of the orbit, the 
dolicocephalic cranium, and the narrow face have 
some influence on the development of this eye. 

DIAGNOSIS. 

The acceptance of a convex glass for distant 
objects is positive proof of hyperopia, and even 
the acceptance of a weak concave glass does not 
disprove it, as frequently the hyperope has spasm 
of accommodation which simulates myopia, and a 
concave glass improves vision, whereas the person 
is really hyperopic. In such cases it is always 
necessary to set aside the power of accommoda- 
tion, relaxing the spasm. To do this, it is fre- 
quently necessary to use a mydriatic for some days, 
applying it several times daily before the spasm 
can be completely overcome. A one per cent solu- 
tion of sulphate of atropine has so far proved the only 
reliable mydriatic in my practice. When the 
spasm is thoroughly relaxed, and the power of 
accommodation is completely under control, it will 
be found that concave glasses no longer improve 
vision, but convex do. 

There are several methods for detecting hyper- 
opia, some of which we here consider. 

Cuignet's Test. One of the readiest means 
without the mydriatic is Cuignefs method, or the 
shadow test — skiascopy, of which we have already 
spoken in Chapter VI. As the light is cast into 
the eye with a flat mirror, the shadow flits over 
the pupil in the same direction that the light is 
thrown, whereas the opposite obtains in myopia. 

Prisoptometry (page 94). Prisoptometry is 
another test, although this is not so accurate as 



HYPERMETROPIA. 163 

the shadow test, because the power of accommoda- 
tion may interfere. If the power of accommoda- 
tion, however, is set aside, the test is reliable. In 
hyperopia the false disc (V, Fig. 81, page 95) is 
separated from the true, and if it is a case of sim- 
ple hyperopia, the space remains of the same width 
all the way around as the prism is revolved. 

Chromatic Test (Plate VII). The chromatic 
test is also convenient for revealing hyperopia; 
the border of the name with this test appears red 
while the center is blue, the reverse being true in 
myopia. The convex glass that will neutralize the 
flame indicates the degree of hyperopia. 

Scheiner's Test (page 127). This consists, in 
brief, in requiring the person to look at a flame 
through a card with two perforations, which must 
be so near together that rays passing through 
them will enter the pupil. In the hyperopic eye, 
two sets of rays will reach the retina before meet- 
ing, each set forming an image of the flame. The 
greater the hyperopia, the further apart will be 
the images formed (Fig. 101, page 128). These are 
projected outwards as crossed images, and the 
patient sees two images of the flame. The convex 
glass which, placed behind the card, causes the flame 
to be seen singly indicates the degree of hyper- 
opia. If a piece of red glass be placed behind the 
right aperture of the card, the left one of the two 
images will appear red, the other one white. The 
opposite obtains in myopia. 

Test with the Ophthalmoscope. This is 
one of the readiest and most reliable tests. If the 
eye is viewed by the ophthalmoscope from a dis- 



164 HYPERMKTROPIA. 

tance of twelve or fourteen inches, -the blood-ves- 
sels at the fundus of the observed eye will seem 
to travel in the same direction in which the ob- 
server moves his head. 

If the eye is viewed from a near point, the 
power of accommodation of both examiner and 
examined at rest, a convex glass will be necessary 
to bring out the details of the fundus distinctly. 
The higher the degree of hyperopia, the stronger 
will be the glass required. The strongest convex 
glass with which you can distinctly see the fine 
blood-vessels at the margin of the disc or those 
near the macula indicates the amount of hyperopia 
and the glass to be prescribed. (See Chapter VI, 
page 96.) 

PRINCIPAL AND MOST RELIABLE TEST. 
Trial Glasses (Fig. 106). The most reliable 
test and the one usually employed by oculists 
is the trial glasses from the trial box. If the 
degree of hyperopia is more than 2 D. or 3 D., a 
convex glass will improve vision. If it is a low 
form of hyperopia, the convex glass frequently does 
not improve but may diminish the vision, while a 
weak concave glass may improve. As above said, 
in such a case the power of accommodation must 
be set aside by mydriasis. However, it is not 
always practicable or safe to employ a mydriatic ; 
as, for instance, those patients who are dependent 
upon their eyes for a livelihood, as seamstresses, 
clerks, book-keepers, teachers, artists, etc., whose 
positions can not be readily filled by others, and 
who, if they are laid off from work for a few days, 
are liable to lose their positions. In such cases, 



HYPERMETROPIA. 



185 



it may be best to ascertain as near as possible the 
amount of hyperopia and prescribe glasses without 
mydriasis. Yet there are many exceptions where 
there is persistent asthenopia, due, perhaps, to some 
hidden heterophoria or astigmatism, which can be 




Fig-. 106. 

revealed only by employing a mydriatic, and in 
these cases the correction and relief to be gained 
by the drug and proper glasses are paramount 
to all other considerations. The drug does 
not only disclose the entire hyperopia, but it 



166 HYPERMETROPIA. 

also acts as a remedy by resting the ciliary 
muscle. Where there is persistent spasm of ac- 
commodation, it is frequently found necessary to 
keep the person under mydriasis for ten days or 
two weeks before the spasm will give way entirely 
and the true condition be revealed. Again, the 
mydriatic is not to be used indiscriminately. In 
middle-aged or old people it may provoke that most 
formidable disease — glaucoma. Yet, as before said, 
it is very important to use it in most cases, espe- 
cially with the young, for if a mistake were made 
and concave glasses used, injury to the eye would 
result. Frequently evils arise, such as cyclitis, cho- 
roiditis, staphyloma, etc., from individuals select- 
ing their own glasses or incompetent dealers select- 
ing for them. 

With the test in question, the patient should 
be placed at twenty feet distant from the test card 
(page 87) and the vision of each eye taken sepa- 
rately, as in myopia. The right eye being tested 
first, the left is covered by an opaque disc, placed 
within the spectacle frame. The amount of vision 
of each eye should be recorded. 

The glass that will give the best vision, the 
power of accommodation being paralyzed, will 
show the degree of hyperopia, and, as a rule, may 
be prescribed. Sometimes, however, it is found 
that the patient will not accept the full correction, 
and only a part of the hyperopia is then to be 
corrected, the remainder to be taken care of by the 
power of accommodation. The left eye should be 
tested in a similar manner to the right. 

Ask the patient to read down the card. Fre- 



HYPERMETROPIA. 167 

quently, if you ask him whether he can see the 
letters on the card, he will answer in the affirma- 
tive, declaring that he can see the smallest; but the 
statement of the patient should never be taken as 
definitive, he should be required to read aloud the 
letters from the top down. Often, we find that 
those patients who say they can see the small let- 
ters have a vision of only fjj, or even much less, 
as fft, or they may see well with both eyes uncovered 
and be blind in one, or the two eyes may vary in 
acuteness of vision. They may be able to see 
same of the smaller letters, but others they will 
miscall; as, for instance, they may call C O, G 0> 
and vice versa; F E or T, etc., which is an evidence 
of a certain amount of astigmatism. These 
patients are sometimes able to see at a glance let- 
ters that become dim if the eye is fixed for any 
length of time upon the card, showing hyperme- 
tropia only partially or momentarily controlled by 
the power of accommodation. The patient then 
should be required to read down the card as far as 
he is able to distinguish the letters ; then a weak 
convex glass, say 0.50, 0.75, or 1 D., should be 
placed before the eye, continuing with stronger 
until the highest number is reached that will give 
the greatest amount of vision. In like manner, 
test the other eye, covering the former with an 
opaque disc. It is my custom to examine always 
the right eye first and make a careful record of 
the vision without the use of glasses, and then the 
amount of sight obtained by their aid. If I use a 
mydriatic, I am careful to record the amount of 
vision without the mydriatic, and the strongest 



168 HYPERMETROPIA. 

glass required to give the greatest amount of vis- 
ion. Then, after the use of the mydriatic, I record 
the vision again without the use of the glasses, 
and then the amount gained by their use. In 
this way, I am able to see at a glance the amount of 
manifest as well as the latent hyperopia, also the 
facultative hyperopia, and the glass giving the 
most benefit. In cases where there are a consid- 
erable amount of asthenopia and other sequelae, 
it is generally more satisfactory to the oculist, and 
usually to the patient's advantage, to use a mydriatic 
at once. However, as has been said, the incon- 
venience and the detriment that may result to the 
person who is dependent upon his eye-sight for a 
livelihood, and who, from being obliged to lay aside 
the work for a time, jeopardizes his position, should 
not be disregarded. 

Mydriasis can be accomplished, usually, by ap- 
prising the patient of its necessity and allowing 
him to arrange accordingly. 

PROGNOSIS. 

Hyperopia can be corrected, but may not be 
entirely cured. In correcting hyperopia, the strain 
is taken off the eye, and the organ is put in a 
better condition for a more perfect development. 
In a low form of hyperopia in a young person, 
we may look for a diminution of the anomaly, and 
a final development to a perfect emmetropic eye. 
I have frequently found this to be true in young 
people, especially school-children and students, 
they in after years by the temporary use of glasses 
becoming absolutely emmetropic. 



HYPKRMETROPIA. 169 

Often in low degrees of hyperopia, especially 
among school-children and students, after the 
school work or the college course is over, and the 
eyes are no longer required for so much continu- 
ous near work, the glasses may be laid aside; but 
if they are not used during the course of study, 
the student suffers from asthenopia and frequently 
has to discontinue his studies. 

SEQUELS. 
As we have said, the hyperopic eye, from its 
anomaly, is of necessity compelled to use the 
power of accommodation for distant as well as for 
near objects. The nearer and smaller the object, 
the greater must be this muscular exertion; and if 
the hyperope is compelled or allowed thus to use 
his eye, complications are liable to follow. By 
the continued effort of accommodation the ciliary 
muscle and contiguous parts are congested; and 
thus dire results may follow. The ciliary muscle, 
from its great effort in heightening the power of 
refraction, is most likely to be affected in one way 
or another. Frequently, we have what is known 
as spasm of accommodation, which causes partial 
paralysis or paresis of the ciliary muscle; and in- 
stead of the lens springing back to its normal 
position and condition when distant objects are 
looked at, the eye is for the time, at least, myopic, 
and may become permanently so, if rest or treat- 
ment is not given. 

Other manifestations of abuse or overuse of 
this muscle present themselves in the form of 
neuralgia, called ciliary neuralgia, pain through the 
temples, over the brows, and deep in the eye. Con- 



170 HYPERMETROPIA. 

vergent strabismus is one of the most frequent 
sequences of this anomaly. 

The hyperope is especially susceptible to dis- 
eases of the appendages of the eye, particularly to 
those of the conjunctiva and the lids. It is now 
a conceded fact that hyperopia is often a primary 
cause of marginal blepharitis, of trachoma, and of 
phlyctenular keratitis ; or, if not a direct cause, it 
exerts its influence in aggravating these affections, 
and prevents a permanent cure if the hyperopia 
be not corrected by glasses. The hyperopic person 
is frequently annoyed by hordeola, chalazia, tra- 
choma, tinea tarsi, ciliary hyperemia; but more 
especially is hyperopia responsible for convergent 
strabismus and heterophoria in many of its forms. 
It is thought to be a frequent cause of that most 
destructive disease — glaucoma. 

Again, it is believed that the hyperopic eye is 
more frequently cataractous than the emmetropic. 

TREATMENT. 

In hyperopia, as in myopia, the eye should not 
be overtaxed and the young child should not be 
allowed to enter school too early. Out-of-door life 
and open-air sports should be encouraged, and 
in-door, sedentary, and studious habits restricted 

The hyperopic eye should be relieved and 
strengthened by the convex glass which corrects the 
anomaly. If the hyperopia is of a low degree, as 
1 D., or a fraction thereof, and in a young person, 
the power of accommodation may be ample to com- 
pensate for the lack of refraction, especially if the 
eyes are not overtaxed; but there is always a higher 



HYPERMETROPIA. 171 

degree of hyperopia than is apparent, the power of 
accommodation concealing a portion. 

Frequently it will suffice to correct the mani- 
fest hyperopia, allowing the accommodation to com- 
pensate for the latent, the patient experiencing 
more comfort when using some muscular effort 
than when he is entirely relieved by glasses. How- 
ever, there are individual cases where, from some 
enervation or from a very weak condition of the 
ciliary muscle, the whole amount — manifest and 
latent — must be entirely relieved, or, in other 
words, the hyperopia in toto must be corrected, 
even though it be of a slight amount. To make 
this correction, the power of accommodation should 
be entirely set aside, and this may not be fully 
accomplished until after the repeated use of the 
nrydriatic for perhaps several days. 

After the degree of anomaly has been ascer- 
tained, the strongest convex glass that will give 
the highest amount of vision should be prescribed, 
and the patient be instructed to use these glasses 
continuously for distant as well as for near objects. 
Especially should this be insisted upon with those 
who have had spasm of accommodation and mus- 
cular asthenopia. With these low forms of hyper- 
opia, heterophoria in one or another form is fre- 
quently associated. This insufficiency of the ex- 
trinsic ocular muscles should be looked for, and, if 
it exists, corrected. (See Chapter XI, Heterophoria.) 

In a high degree of hypermetropia, it is best 
to correct some, at least, if not all, of the latent, 
as well as the « manifest. The patient will not, as 
a rule, accept the full correction at first. Then it 



172 HYPERMETROPIA. 

may be best to correct the manifest and perhaps 
some of the latent, allowing him to wear the glassses 
for a time until his power of accommodation shall 
be so relaxed as to permit of the full correction. 
The strength or condition of the ciliary mus- 
cle or power of accommodation must be taken into 
consideration, whether all or a portion of the latent 
hyperopia be corrected. If this facultative accom- 
modation is well pronounced, as in the following 
case, it is only necessary to correct the manifest: 

Case. The patient was a young lady, M. J — , 
aged twenty, blue eyes, perfect physique, weighing 
130 pounds, a school teacher from Sioux Falls, South 
Dakota, who visited me August 19, 1890, com- 
plaining of pain in and about the eyes, especially 
through the temple and over the brow, and of not 
being able to read for any length of time without 
the lines blurring and letters running together, 
but more especially did she complain of frontal 
and temporal headache. Examination revealed V. 
R. E. ffo V. L. E. H; with plus 0.50 D., vision of 
either eye equaled -|#; she could also get with plus 
1.50 D. $$. Ophthalmoscopic examination, how- 
ever, showed a much higher degree of hyperopia, 
which had been concealed by the dynamic refrac- 
tion. A one per cent solution of sulphate of 
atropine was dropped into the eyes, and under the 
full effect of the mydriatic the vision was again 
taken. I then found that the patient had to come 
within five feet in order to see the largest letter 
on the card with either eye; or, in other words, 
that the static refraction or her real vision, uncon- 
trolled by the power of accommodation, was only 



HYPERMETROPIA. 



173 



^. With a plus 5.50 D. combined with plus 0.25 
D., C- 90°, for either eye, vision was ff 

In slight degrees of static refraction the dy- 
namic refraction is usually sufficient to compensate 
or neutralize the hyperopia, but in higher degrees 
we do not expect it. In the case in question nearly 
the whole amount of hyperopia by an effort of ac- 
commodation could be corrected, and the eye ren- 
dered, as it were, emmetropic. Now, if we grant that 
there was a manifest hyperopia of 0.50 D., we still 
have here a dynamic refraction of 5 D., all of 
which was corrected by the power of accommodation. 

At another examination of this patient August 
25, 1890, vision of either eye was f$, but at this 
date she could relax the dynamic refraction suffi- 
ciently to still get -§£ with a plus 3 D. 

In prescribing glasses for this patient I only 
gave plus 2 D., combined with plus 0.25 D., cylin- 
der, axis in 90° for each eye, allowing her to still 
use more than half of her dynamic refraction; and 
these glasses have, up to this time (1900), given 
perfect satisfaction. Had the dynamic refraction 
been less with the same degree of static refraction, 
I should have prescribed a much stronger glass, 
and in all probability the patient would have re- 
quired a stronger one 

Formerly it has been my custom not to correct 
the full amount of dynamic refraction, allowing a 
portion to be supplemented by the power of accom- 
modation for a time, at least, after which the full 
correction was frequently given. It is, as yet, a 
debated question whether the full correction should 
be given at first, thus compelling the patient to 



174 HYPERMETROPIC. 

adapt himself to the use of the glass of full cor- 
rection at once, or correcting a portion at different 
times as the latent gradually becomes manifest. 

Of late, I have been inclined to believe that, 
as a rule, it is best to correct the full amount at 
once, rendering the patient emmetropic, as it were, 
compelling him to exercise his power of accom 
modation only for near objects or divergent rays 
as the emmetrope does; as sooner or later the full 
correction has to be made, and we thus save time 
and expense to the patient and much vexation of 
spirit to the oculist; besides, the patient is relieved 
in a much shorter time of his asthenopia than if 
the time be prolonged before the full correction is 
given. However, no fast and fixed rule can here 
be adhered to, and the oculist may use his judgment 
in determining what to do. The patient will fre- 
quently object, at first, to the full correction, but if 
he will persevere in the use of these glasses, they 
will prove eventually more satisfactory than those 
partially correcting; the asthenopic symptoms sub- 
siding, the glasses will be worn with much satis- 
faction. 

It would seem that many hyperopic eyes in their 
normal condition demand that a certain amount of 
static refraction be used for all objects — distant as 
well as near, and if the full correction is given, the 
person will complain of asthenopic symptoms, and 
this glass of full correction does not give satisfac- 
tion; but if a weaker one is given, correcting in' 
part the hyperopia, the eye being allowed to use 
some of the static refraction for distant objects 
which it seems to demand, satisfaction is given. 






HYPERMETROPIC. 175 

It is always advisable, if possible, to bring the 
two eyes up to the same degree of vision, and with 
the same strength of glass, prescribing, if possible, 
the same strength of glass for each eye, rather 
than a slight difference between the two. How- 
ever, in anisometropia each eye must be fitted 
irrespective of its fellow. As more or less astig- 
matism is liable to exist with hyperopia, one 
should always look for it, and, if there is any, cor- 
rect, the same If, however, a spherical glass, with 
the power of accommodation set aside, will give f#, 
there is no need of cylinders. However, where a 
cylinder will give f# it frequently has the effect of 
relieving the asthenopia, whereas a spherical glass, 
giving the same amount of vision, will fail to relieve 
the asthenopia. 

In adjusting glasses to the hyperope, as in 
other forms of ametropia, especially with high de- 
grees, care should be exercised in fitting them to 
the face; they should be accurately centered ver- 
tically as well as horizontally (unless decentration 
is desired for its prismatic effect). In strong con- 
vex glasses the least inclination in the plane of 
the glass produces an astigmatic effect, and any 
slight decentration will produce the effect of a 
prism, and may cause heterophoria. 

In a high degree of hyperopia, it is advisable, 
in some cases, to prescribe two pairs of glasses, a 
weaker for distant and a stronger for near. From 
distant objects, the rays of light meet the eye as 
parallel, and their focus, as they pass through the 
dioptric media, is in front of the focus for rays 
coming from near objects which are divergent; 
and hence, the former condition would not require 



176 HYPERMETROPIC. 

so strong a glass as the latter. But, if the power 
of accommodation is good and the eye rendered 
emmetropic by a glass, there is no further need 
of a second pair. 

By the many examinations made of the eyes 
of school-children, soldiers, and babies, it has been 
found that the per cent of hyperopia is much 
larger than that of emmetropia, and some have 
concluded from this that the moderately hyperopic 
eye is to be looked upon as the typical or normal 
eye, rather than the emmetropic. 

Dr. Roosa says that in case of compound hyper- 
opic astigmatism of a low degree, he corrects the 
astigmatism only, leaving the hyperopia to the 
power of accommodation. I have frequently no- 
ticed myself that in a low degree of compound 
hyperopic astigmatism, if I correct both, giving a 
sphero-cylindrical glass, this glass does not always 
prove satisfactory; and if I change, correcting only 
the astigmatism with a simple cylindrical glass, 
this glass is worn with much satisfaction; as, for 
instance, in a case of compound hyperopic astigma- 
tism, say 0.50 D. in the vertical (90°) and 1 D. in 
the horizontal meridian (180°), instead of giving a 
0.50 D. spherical combined with 0.50 D. cylinder 
with axis of the cylinder in the 90th meridian, I 
simply prescribe the cylinder, leaving the 0.50 D. 
of hyperopia uncorrected. But in a higher degree 
of hyperopia with astigmatism, simply correcting 
the astigmatism will not suffice. 

Although we may feel that it is oftentimes advis- 
able to deduct from the glass of full correction in 
simple hyperopia or myopia, we would never think 
of making any deduction from the cylinder required 
to correct the astigmatism. 



CHAPTER IX. 



ASTIGMATISM. 



As has been stated in Chapter IV, the anom- 
alies of refraction are of two kinds; namely, my- 
opia and hyperopia. In these two forms we find 
that the anomaly is of the same kind and amount 
throughout all the different meridians of the eye. 
There are eyes, however, which are emmetropic in 
one of the principal meridians while the other is 
ametropic. Again, there are others which have 
some form of ametropia in both principal merid- 
ians, but of a greater amount in one than in the 
other. Still, there are others in which one merid- 
ian is of one form of ametropia, while the oppo- 
site is of the other form. 

These phenomena are due to a non-symmetri- 
cal curvature of the cornea, sometimes of the crys- 
talline lens, and this asymmetry of curvature is 
called astigmatism. The term signifies that rays 
emanating from a point are not reunited at a point ; 
or, in other words, the refractive media of the eye 
are not equal in all their meridians, the focal dis- 
tance of one being greater than that of its oppo- 
site ; that is to say, the refractive meridians are not 
symmetrically arranged around one axis. 

Astigmatism was accidentally discovered by 
Young, when, looking through the telescope, he 
noticed that the hair-line or wire stretched across 

177 



178 ASTIGMATISM. 

the instrument was seen only in certain meridians 
as the telescope was revolved. 

If astigmatism be of the cornea it is called corneal 
astigmatism; if it is of the lens, it is called len- 
ticular. All eyes, however, as has been proven by 
Donders, are slightly astigmatic, since the cornea 
in the so-called normal or emmetropic eye does 
not refract equally in all its meridians, and the 
focal distance is generally shorter in the vertical 
than in the horizontal; and on this account, fine 
vertical lines are seen at a further distance than 
horizontal ones, and the latter can be seen closer 
than the former. This proves the above state- 
ment that the points of the refracting meridians 
are not symmetrically arranged around one axis. 

In speaking of the principal meridians in con- 
nection with astigmatism, we usually mean the 
90th and the 180th, as these are the ones that are 
most frequently in error; however, the principal 
meridians may be at almost any degree, but the 
two erring meridians are always at right angles to 
each other unless it be irregular astigmatism, 
which can not be corrected. If one meridian is 
at 45°, the other must be at 135°; if one is at 75°, 
the other is at 165°; if one is at 105°, the other is 
at 15°, etc. A slight difference in the two principal 
refracting meridians in the so-called emmetropic 
eye is to be disregarded, needing no correction; 
but if the difference is considerable, it will provoke 
asthenopic symptoms and should be corrected. 
Astigmatism is quite a frequent anomaly, and is 
often responsible for asthenopia. • 



ASTIGMATISM. 



179 



The following figures illustrate this anomaly. In 
Fig. 107 we imagine the light to come from a 
given point (L), and pass through the refractive 
media, being focused somewhere on the axis behind. 




Fig. 107. 



We consider here only the vertical (VV) and 
the horizontal (HH) meridians, which we shall call 
the principal meridians. Rays of light coming 
from L (Fig. 107) would meet the eye as a cone of 
light, and we find that the rays which, pass through 
the vertical meridian (VV) are converged more 
rapidly than those that pass through the horizontal 
(HH), while both are approximating the axis. 
Those of the vertical meet the axis in front of those 
of the horizontal, and before either meet we have 
the elliptical figure A (Figs. 107 and 108). 




OD^ hh ^**^ i> h ® b h ® b h \ h 



Tig. 108. 

A little further on the vertical have intersected, 
while the horizontal are still some distance apart, 
and we have the horizontal line, B. Beyond this 
point, the vertical diverge, the horizontal ap- 
proach, and there is a small horizontal ellipse, 
C Beyond this point, nearer the retina, the ver- 
tical are slightly more divergent, while the hori- 



180 ASTIGMATISM. 

zontal are nearer together, the distances between 
the divergent vertical and the convergent horizon- 
tal are eqnal, and the circular figure, D, results. 
Still further on, the vertical are more divergent, 
the horizontal are more approximated, and we have 
the vertical elliptical figure, E. Further on, the 
horizontal have come to a focus and the vertical 
are more separated, and we get a vertical line, F. 
Still beyond this point, both vertical and horizon- 
tal diverge, and a large vertical ellipse, G, is the 
result. . 

The interval between the points of intersection 
of the vertical and that of the horizontal is the 
focal interval {pm, Fig. 107). At the center of the 
focal interval, the amount of divergence of the 
vertical equals the amount of convergence of the 
horizontal, and consequently the rays form a small 
circle. The astigmatic person regulates his power 
of accommodation so as to bring the middle point 
of the focal interval upon the retina, and so gets 
the smallest circle of diffusion. At the very best, 
the image is not sharp, as there is no true focus, 
there being only small circles of diffusion. The 
image is more distinctly seen here than at the 
anterior or posterior extremity of the focal interval. 

In Figure 108 the letters A, B, C, D, E, F, and 
G correspond to the same letters in Figure 107. 
The rays which lie in the plane of the vertical 
meridian (VV, Fig. 107) are brought to a focus at 
o y while the rays which lie in the plane of the 
horizontal meridian (HH) are not yet united, but 
form the horizontal line hk } the anterior focal line. 
The rays in HH are united further back at m, 



ASTIGMATISM. 181 

where the vertical rays form the vertical line vv, 
the posterior focal line. The aberration which is 
due to a difference in the focal distance of the two 
principal meridians is called regular astigmatism^ 
and depends upon the curvature of the cornea, 
whereas the aberration which is due to a difference 
in the refraction in one and the same meridian is 
called irregular astigmatism, and is usually due to 
ulceration of the cornea or a peculiar condition of 
the lens. This form can not be corrected by glasses 
and it frequently gives rise to monocular polyopia. 

The greater the difference in the refraction of 
the principal meridians the greater will be the 
circles of diffusion, and consequently an increased 
indistinctness of vision. If there is much astig- 
matism, the acuteness of vision is impaired for 
both near and distant objects. 

Regular astigmatism is of three forms; namely, 
simple ■, compound, and mixed. 

Simple astigmatism is where one of the prin- 
cipal meridians is emmetropic and the other ame- 
tropic (either myopic or hyperopic). 

Compound is where both are either myopic or 
hyperopic, but one meridian is of a higher degree 
of ametropia than the other. 

Mixed astigmatism is where one of the principal 
meridians is myopic, the . other hyperopic. Either 
the myopia or the hyperopia may predominate. 

CAUSE. 

Astigmatism is usually congenital, frequently it 
is hereditary. Occasionally it follows an operation 
for the extraction of cataract, or it may be a sequel 



182 ASTIGMATISM. 

to traumatism of the cornea. Astigmatism occur- 
ring after the extraction of cataract may be due to 
the removal of the lens, which, from its asymmetry 
previous to the extraction, corrected the asymme- 
try existing in the cornea. It has also been noticed 
that astigmatism has been corrected after the ex- 
traction of cataract, showing that the astigmatism 
was of the lens and not of the cornea. Lenticu- 
lar astigmatism, however, is very rare. 

The usual cause of astigmatism after extraction 
of the lens is due to the change of the curvature 
of the cornea from the union of the wound, espe- 
cially if there has been imperfect coaptation of the 
lips of the wound after extraction. 

It is thought that the location of the incision 
as to whether it is scleral or corneal influences the 
amount of astigmatism. 

Ulcers, abrasions, wounds, etc., of the cornea are 
among the causes of irregular astigmatism. 

SYMPTOMS. 

The vision of a person with astigmatism of 
any considerable amount is below the normal. The 
astigmatic person is frequently in the habit of 
holding the head to one side in order to gain a 
sharper and more distinct image of the object. 
He frequently complains of frontal and temporal 
neuralgia. He refers the pain more especially to the 
deep parts of the eye, the back of the eye, and with 
the ophthalmoscope there can almost always be 
seen some pulsation of the veins at the disc, evi- 
dencing intraocular tension. 



ASTIGMATISM. 



183 



Astigmatism is thought to be responsible for 
epilepsy, vertigo, and different forms of chorea, 
more especially that form in which there is spasm 
of the facial muscles — a peculiar twitching and 
jerking of the face, corners of the mouth, and 
muscles of the lids. Statistics show that the ma- 
jority of inmates of the insane asylums and prisons 
have some form of ametropia or heterophoria. 

Astigmatism is evidencedby "nervousness" , irrita- 
bility, uneasiness, and discontentedness ; especially 
is this the case if the astigmatism is in other than 
the vertical or the horizontal meridians. 

With the ophthalmoscope (concave mirror), by 




Fig. 109. 

the direct method, viewing from a distance of 
twelve or fourteen inches, the retinal vessels appear 
more distinct in a certain meridian than elsewhere; 
and if it is a case of hyperopic astigmatism, they 
seem to travel in the same direction that the head 
of the observer is moved; the reverse is true in 
myopic astigmatism. If the eye is approximated, 
and the fundus viewed by this method, the disc, 
instead of appearing circular, is seen oval, and its 
longer diameter may be in any meridian (Fig. 109); 



184 



ASTIGMATISM, 



it may be in the vertical, horizontal, or any merid- 
ian between these two. 

If it is myopic astigmatism, the disc by this 
method always appears larger; but if viewed by the 
indirect method, the disc appears smaller, whereas 
the reverse is true of hyperopic astigmatism. 
Where the patient refers the pain especially to the 
eyeball or to the back of the ball, I have almost 
invariably noticed pulsation of the veins near their 
entrance to the disc. In fact, this may be taken as 
pathognomonic of astigmatism. 

DIAGNOSIS. 
It is not, as a rule, difficult to recognize this 
anomaly. In the diagnosis, a settled line of exami- 
nation must be adhered to, or great confusion will 
arise. 




In the first place, we must carefully ascertain 
the acuteness of vision. If it is below M, the nor- 



ASTIGMATISM. 



185 



mal standard, we should try to raise it with, a con- 
cave or a convex glass. If we fail in doing so, 
astigmatism may be suspected. Have the patient 
look at the dial (Fig. 110) twenty feet away. If 
he is astigmatic, lines in a certain meridian will 
appear brighter and more distinct than in others. 
If it is a case of simple hyperopic astigmatism 
(the hyperopia being in the horizontal meridian), 
the lines, as a rule, w r ill appear more distinct in 
the vertical or near the vertical than in the hori- 
zontal. However, the reverse may be true, which 
is against the rule. In case of simple myopic 
astigmatism (the myopia being in the vertical 




Fig. 111. 

meridian), the person usually sees the lines in the 
horizontal or those near the horizontal brighter 
and more distinct than those in or near the ver- 
tical; but the reverse, as in the former case, may 
be true, which is also contrary to the rule. The 



186 



ASTIGMATISM. 



Fig. 112. 



astigmatic person makes mistakes 
in some letters ; for instance, lie 
calls G C or O, Y T or V, O C, 
N H, B R, and vice versa. This 
shows that only parts of the letters 
which are in certain meridians come 
ont distinctly. 

The astigmometer {ophthalmome- 
try) is an incontrovertible means of 
recognizing corneal astigmatism, 
and it also indicates the meridian; 
it does not only this, but in many 
cases it approximately shows the 
amount without a mydriatic. It is 
also a means of measuring the ra- 
dius of the cornea. The Javal and 
Schicetz ophthalmometre (Fig. Ill) 
is the most scientific instrument 
for this purpose yet placed in the 
hands of the ophthalmologist. 

It consists of a large disc spaced 
off by meridians into degrees from 
1 to 180 from above (0) downward 
to the right, and from below upward 
to the left, making 360° altogether, 
and has concentric circles one degree 
apart, the radius of the disc being 
divided into 45 degrees. The fig- 
ures on the disc are inverted, but 
as seen reflected from the cornea 
are upright. The disc is supported 
on a tripod, and through its center 
is placed a telescope containing a 



ASTIGMATISM. 



187 



Nicolas prism (B, Fig. 112) and two bi-convex 
lenses (A and C), which have the effect of doubling 
the image. At the extremity of the telescope is 
an ocular (D) and two crossed wires, both of which 
are seen distinctly when the instrument is in fo- 
cus. In front of the disc upon the telescope is 
attached a curved, horizontal 
bar (Fig. 113) having a radius 
of curvature of 27 cm. 

By this arc we are able to 
measure the radius of curvature 
of the cornea. Upon the arc 
are placed two plaques (A and 
B, Fig. 114) and a pointer (C). 
The plaque A is divided into 
steps. The pointers bb extend- 
ing from the plaques show the 
axis of the cylinder in hyper- 
metropia; and if myopia exists 
the long pointer C marks the 
axis. 

In front of the disc and 
about fourteen inches away is 
an adjustable chin-rest or frame, 
to which may be attached the 
electric or gas light. The in- 
candescent electric light is the 
best, as it does away with the 
objection of heat from the gas 
light. 

The patient under examina- Fig. us. 

tion should direct the eye steadily upon the telescope,, 
the other being covered by an opaque disc. The 




188 



ASTIGMATISM. 



forehead should rest firmly against the frame and 

the. head be supported by the chin-rest (Fig. 115). 

//^" lv <\ The disc with 

its division and 
the two plaques on 
the horizontal bar 
(Fig. 115) are seen 
by the observer 
through the tele- 
scope as reflected 
from the cornea. 
The prism has the 
Fi &- 114 - effect of doubling 

the images, and the two plaques on the bar are 



l 




! 


a 






3 


< 


> 






I. 






i 






/ne r/roH/fZ. 


^ 


T7 
// 

y/ 
c 


o 








Fig. 115. 



ASTIGMATISM. 



189 



seen as four; the two central ones are the ones to 
be regarded (Fig. 116). The plaque with the steps 
is movable, and when the instrument is in focus, 
this should be moved up so that the edge of the 
notched parallelogram touches the edge of the 
other, and that the horizontal line of one is con- 
tinuous with the other, ad. If the lines cannot be 
made to be continuous, it suggests a conicity of 
the cornea and irregular astigmatism. 

After the adjustment of the instrument and the 




Fig. 116. 

plaque, turn the telescope with the bar, and if the 
two plaques remain tangent throughout the differ 
ent meridians as the telescope is rotated, there is 
no astigmatism indicated; but if the steps overlap 
the other plaque in a certain meridian, astigmatism 
exists, and the pointers indicate the meridian. 



190 



ASTIGMATISM. 



The overlapping of one step indicates 1 D. of ame- 
tropia. With this instrument it is possible to 
ascertain even a very slight amount of astigma- 
tism, as a slight overlapping of the step, as one- 
fourth, would indicate 0.25 D., providing the instru- 
ment is accurately and well made (if not, it is 
unreliable and misleading). 

Often, winking or closing the lids, thus vary- 
ing their pressure upon the cornea, changes its 
curvature, giving an illusive impression of astig- 
matism. 

In a case of simple astigmatism, the plaques 
may be seen as tangent in the horizontal meridian 
while the steps overlap in the vertical (Fig. 116); 
or they may separate as in Fig. 117. 




Fig. 117. 

In using the instrument, good illumination is 
imperative. Sunlight is the best; but to make the 
instrument useful in all weather, artificial light 
should be provided, and this light should be on a 
level with the bar, and reflected by shades, so as 
to thoroughly illuminate the whole disc. It is 
imperative that the patient's head be properly sup- 



ASTIGMATISM. 191 

ported by the chin-rest and the frame, and that the 
eye be held perfectly still, as the slightest movement 
will throw the image ont of focus, and false impres- 
sions be received. 

F. A. Hardy & Co., of Chicago, manufacture an 
astigmometer, constructed optically on exactly the 
same principles as the Javal & Schicetz instrument, 
differing only in the arrangement of the arc carrying 
the mires, and the substitution of a perfectly plain 
disc, which rotates with the arc, in place of the sta- 
tionary graduated disc employed on the Javal & 
Schicetz instrument. The advantages of this mode 
of construction are that the arc, being centrally 
attached to the tube which carries it, always remains 
at the angle at which it is turned and does not fall 
out of position when the operator releases it, and 
the operator also is not confused by the multiplicity 
of images produced by the reflection of the disc on 
the French style, but obtains a perfectly clear image 
of the mires, which is the practical part of the 
instrument. They also abandon the cross-hairs for 
focusing the eye-piece, since the focusing of the eye- 
piece is a correction of very little value in the use of 
the instrument, the effect of an error of one dioptre 
in the eye of an observer being equal only to about 
y J o P ar t of a dioptre in the reading of the astigmom- 
eter, and by removing the cross-hairs an obstruc- 
tion to the view of the mires is eliminated. The 
graduations indicating the position of the principal 
meridian are on a supplementary arc, which enables 
the operator to read off the meridian from the posi- 
tion last assumed in the test, instead of being 
obliged to note the meridians during the examina- 
tion of the cornea. (See Fig. 188, page 289.) 



192 ASTIGMATISM. 

Test for Determining the Presence op 
Astigmatism by the Prisoptometer. The pr- 
optometer (Fig. 80) consists of a double prism set in 
a semi-circular disc, which is spaced off by meridians 
ten degrees apart. It is supported on a standard 
which is clamped to the table. The double prism 
has the effect of doubling the image of the object 
looked at. The white disc (page 95) on a dark back- 
ground seen at sixteen feet by the emmetropic eye 
through the double prism is doubled and the images 
are tangent throughout all the meridians as the 
prism is rotated. In the ametropic eye the images 
are not tangent, but they overlap or separate accord- 
ing to the form of ametropia (myopia or hyperopia). 

In examining for astigmatism, place the patient 
behind the prisoptometer sixteen feet from the disc. 
Revolve the prism and notice by the pointer on the 
instrument at which meridian the false image is 
tangent to the other. Then turn the prism around 
one way or the other, and if there is astigmatism, 
the false image, in shifting its position, will either 
overlap the other or separate from it, according to 
whether it is myopic or hyperopic astigmatism, the 
pointer indicating the meridian. This is a ready 
means of detecting astigmatism, and the amount 
can be ascertained by placing a lens in the clip in 
front of the dial of the instrument. If it is a case 
of myopic astigmatism, the concave glass that 
will distance the two images so as to make 
them tangent will indicate the amount of astigma- 
tism and the glass to be prescribed. If it is a case 
of hyperopic astigmatism, the strongest convex 
glass that will approximate the two images so 



ASTIGMATISM. 193 

as to render them tangent will show the amonnt of 
hyperopia 

Care must be taken that the eye being examined 
look directly through the prism and that the head 
be steadied; also that the disc looked at be parallel 
with the dial and directly in front of and of the 
same height as the prism, and exactly sixteen feet 
away. If the distance be more than sixteen feet, 
an emmetropic eye appears hyperopic and a myopic 
eye might appear emmetropic. If the disc stands 
obliquely to the instrument, astigmatism is falsely 
indicated. A spherical glass can be used for ascer- 
taining the amount of astigmatism and a corre- 
sponding number in a cylinder must be prescribed 
with the axis in the meridian of emmetropia. 

Test by THE Keratoscope. The keratoscope 
(Fig. 79) consists of concentric rings on a disc 
with an opening through the center. This instru- 
ment was the foreshadowing of the Javal & Schicetz 
ophthalmometre and is an objective test based upon 
scientific principles. Place the patient with his 
back to the window, or to an artificial light, and 
then, with the disc in front of your eye, view the 
cornea of the patient's through the opening from 
a distance of about one foot. A magnifying glass 
placed back of the disc may or may not be em- 
ployed. If used, it magnifies and sharpens the 
image. The concentric rings of the disc will be 
mirrored upon the cornea, and will, of course, 
appear very much smaller on the cornea than 
they are on the disc. If they are circular, no 
astigmatism is indicated; but if they are oval, 
astigmatism of the cornea is present, and the 



194 ASTIGMATISM. 

longest diameter will indicate the meridian of 
astigmatism. However, great care mnst be taken 
in employing this test, for if the opening of the 
disc is not of the same height as the pupil and 
the disc parallel with the plane of the iris, the 
rings may appear oval, thus simulating astigmat- 
ism ; or, if the opening in the disc is not perfectly 
circular, this would also give rise to false im- 
pressions. 

Test by the Chromoscope. The chromo- 
scope (Fig. 121) consists of a card two feet 
square with a dial or face spaced off into merid- 




Fig. 121.— Chromoscope. 

ians. In the center of the dial is a circular open- 
ing three-eighths of an inch in diameter, also a 
rotating ring having an indicator through its 
diameter extending across the circular opening. 
This indicator turns with the ring. 

In examining with this instrument, place the 
patient at a distance of twenty feet, covering the 
eye not to be tested with an opaque disc. Then 
place the chromatic glass (Fig. 122) in front of 
the eye being tested. If the light through the 



Plate VIII. 




# 








ASTIGMATISM. 195 

-opening appears circular, no astigmatism is indi- 
cated; but if it is elongated, astigmatism is pres- 
ent. In emmetropia the circle will be of a diffuse 
violet tint (A, Plate VIII) ; in Hyperopia it will 
liave a blue center and a 
red border (B) ; and in 
myopia the center will 
appear red and the border 
blue (C). 

In simple hyperopic as- 
tigmatism, the circle is 
elongated, having a blue 
center and red extremities 
(D) or a crossed figure, Fig. 122. 

the blue extending out from each side (E). Ro- 
tate the indicator to the longest axis of the figure, 
and read off from the dial the meridian of as- 
tigmatism. The strongest convex cylinder that 
will render the figure circular gives the amount 
of astigmatism. In simple myopic astigmatism 
the elongated figure has a red center with blue 
extremities (F); the longest axis indicates the 
meridian of astigmatism. 

G shows the appearance in mixed astigmatism, 
where the degree of hyperopia is greater than the 
myopia; the red is longer and narrower, while 
the blue part crossing it is shorter. The direc- 
tion of the red bar indicates the meridian of 
hyperopia, and the blue the meridian of the my- 
opia. Where myopia predominates, H shows the 
appearance. It is an elongated, narrow blue bar 
with a red center. The longest axis of the bar 
indicates the meridian of the myopia. 



196 ASTIGMATISM. 

In irregular astigmatism the cross is not right- 
angular, being in some cases a Maltese cross (I)> 
or the bar is not of the same width throughout 
(K). If the myopia predominates, there is only 
a bar ; if the hyperopia predominates, there is a 
cross. 

Astigmatism as Detected by the Ophthal- 
moscope. The ophthalmoscope, as in the simple 
forms of ametropia, is one of the readiest and 
most reliable means of detecting astigmatism. 
By the direct method, where the eye is viewed 
from a distance of twelve or fourteen inches, the 
retinal vessels appear more distinct in a certain 
meridian than they do in the opposite one, and 
the latter is the meridian of astigmatism. If the 
eye is viewed from a near point, say an inch or 
two away, the optic disc will be seen of an oval 
form; and the higher the degree of astigmatism 
the more will the disc appear elongated. The 
blood-vessels in the longer diameter are more dis- 
tinct thari those at right angles; and if it is a 
case of simple hyperopic astigmatism, the strong- 
est convex glass that will bring the blood-vessels 
distinctly into view will indicate the amount of 
astigmatism ; or, if it is a case of simple myopic 
astigmatism, the weakest concave glass that will 
bring them into view will indicate the amount- 
If it is a case of compound astigmatism, glasses 
of different strengths must be used in the princi- 
pal meridians. If it is mixed astigmatism, say 
hyperopia of the vertical and myopia of the hori- 
zontal, then the strongest plus glass that will bring 
the vessels distinctly into view in the vertical, 



Plate IX. 



T 




"A. 



j~/ 



ASTIGMATISM. 197 

and the weakest minus glass that will bring them 
into view in the horizontal, will show the amount 
of each kind of astigmatism. If the eye is exam- 
ined by the indirect method, the image of the 
myopic eye is always reduced. 

Retinoscopy, Skiascopy (page 118). This is a 
ready and reliable test, and for children it is one 
of the most satisfactory, convenient, and speedy 
means. The pupil should be dilated, and the 
patient placed in a dark room with the light im- 
mediately above his head. With a flat mirror, 
at a distance of three feet, the examiner reflects 
the light into the pupil (Plate IX). If it is sim- 
ple hyperopia, the shadow will travel in the same 
direction that the mirror is tilted'; if it is simple 
myopia, it will travel in the opposite direction. 
In simple astigmatism the shadow will be seen only 
in the meridian of ametropia; if it is compound 
astigmatism, the shadow will be sharper in one 
principal meridian than in the other. If the 
astigmatism is in a meridian other than the verti- 
cal or the horizontal, the shadow will appear in 
this meridian, and although the light be thrown 
from above downward, the shadow, instead of trav- 
eling from above downward, will go in an ob- 
lique direction. 

If it is a case of mixed astigmatism, the 
shadow will go with the mirror in one meridian, 
and against it in the other. 

The lens that will neutralize or dispel these 
shadows indicates the amount of astigmatism, 
and the glass to be prescribed. (See page 124, 
Chap. VI.) 



198 ASTIGMATISM. 

Test by Trial Glasses from Trial Box.. 
Although we may employ these other different 
tests,, we never feel quite warranted in prescrib- 
ing glasses without making a corroborative test 
by means of the trial glasses from the case — the 
test generally used. 

Examination by this method is conducted in 
the following manner: The patient is placed in 
front of Snellen's card at a distance of twenty 
feet. Adjust the trial frames and see that they 
are properly poised so that the patient will look 
through the center of each opening. Cover one 
eye, say the left first, with an opaque disc, and 
get the vision of the right, recording the same. 

If the patient is able to see only the larger 
letters, or part way down the card, try both plus 
and minus spherical glasses. If the spherical 
glass does not give perfect vision, nor improve it, 
astigmatism may be suspected. Place a stenopaic 
disc with a narrow slot in front of the eye, and 
rotate the slot through the different meridians, 
finding the meridian of the best vision. If the 
meridian is found through which vision is 
!$, or normal, and no glass improves, we have 
a case of simple astigmatism. If the stenopaic 
disc is now rotated to the opposite meridian, 
vision may be much below the normal. If so, 
find the strongest convex spherical or the weak- 
est concave spherical glass that will give the 
greatest amount of vision in this meridian. If a 
convex glass improves the vision, we have sim- 
ple hyperopic astigmatism. If a concave improves, 
it is simple myopic astigmatism. (Right here 



ASTIGMATISM. 199 

let us observe that in spasm of accommodation, 
simulating myopia, slight concave glasses will im- 
prove vision, whereas hyperopia really exists. 
In these low forms of astigmatism, it is abso- 
lutely necessary that a mydriatic be employed, 
lest the real, true condition be over-looked and a 
false glass prescribed.) 

In case that no meridian is found where vis- 
ion is M, we may suspect either compound or 
mixed astigmatism. In such a case we rotate 
the slot to the meridian of best vision, and find 
the plus or minus glass that gives the greatest 
amount of improvement in that meridian. Then 
rotate the slot to the opposite meridian and find 
the plus or minus glass that gives the greatest 
amount of vision in this meridian. If a convex 
glass improves in both meridians, it is compound 
hyperopic astigmatism; but if a concave of con- 
siderable strength is required, it is a case of 
compound myopic astigmatism. If one meridian 
is improved by a convex glass and the other by a 
concave, this shows mixed astigmatism. 

PROGNOSIS. 

Astigmatism, like other forms of ametropia^ 
can be corrected by the use of glasses, but can 
not be cured. Frequently proper glasses adjusted 
in a case where the vision is so low as scarcely 
to enable the person to get about, give most 
happy results, and it is very gratifying to see 
the expressions of surprise and delight come 
over the faces of these persons as a new world is 
opened to them by the correction of their anomaly. 

By the correction of astigmatism, the eye 



200 



ASTIGMATISM. 



grows stronger and the vision becomes more 
acnte. Not infrequently is it impossible to find 
a glass that will give an approach to perfect 
vision; but oftentimes if the glass that affords the 
most improvement is worn for a time, the eye 
will so develop that at a subsequent time a glass 
may be found that will give still better vision, even 
to? or the normal. 

TREATMENT. 

Until very recent times, it has been the custom 
of ophthalmologists to ignore the lower forms or 
a slight amount of astigmatism, correcting only 
the myopia or the hyperopia, but not always with 
the relief and satisfaction desired. It is now found 
that the slightest amount of astigmatism is often 
responsible for the most serious affections. Fre- 
quently, this slight amount of astigmatism is so 
concealed by the power of accommodation that it 
is overlooked, and it is only with the most care- 
ful and searching examination that it is revealed. 

Hypothetical Cases. First. — Let us imagine 
a case of simple hyperopic astigmatism where 
the vertical meridian is emmetropic; i. e., the 
patient, when the slot is rotated into this merid- 
ian, is able to see \%\ but when it is rotated into 
the horizontal meridian he only gets H, and re- 
quires a convex glass of 2.50 D. to bring the vis- 
ion to \%. This is simple hyperopic astigmatism 
of 2.50 D. in the horizontal meridian. To cor- 
rect this, we prescribe a convex cylinder of 2.50 D., 
axis in the 90th meridian. 

Second. — Let this be a case of simple myopic 
astigmatism, where, for instance, if the disc is 



ASTIGMATISM. 201 

rotated into the 180th meridian, the vision is M; 
but in the 90th meridian vision is toV, and re- 
quires a minus 3.50 D. to bring it to H- We 
have here a case of simple myopic astigmatism of 
3.50 D. in the 90th meridian. To correct this, 
we prescribe a concave cylinder of 3.50 D. with 
axis placed in the 180th meridian. 

Third. — Let this be a case of compound hyper- 
opic astigmatism, where we find that in rotating 
the slot the vision is best in the 75th meridian, 
and a convex glass of 2 D. is required to gain 
the highest amount. Now, if the slot is rotated 
into the opposite meridian, the 165th, it requires 
a convex glass of 3.50 D. to get the greatest 
amount of vision. We have here a case of hyper- 
opia of 2 D. with hyperopic astigmatism of 1.50 D. 
in the 165th meridian. In this case we prescribe 
a convex spherical glass of 2 D., which corrects 
the hyperopia, and a convex cylinder of 1.50 D., 
axis of cylinder in the 75th meridian. 

Fourth. — Compound myopic astigmatism. In 
this case we will imagine the greatest amount of 
vision to be in the 15th meridian, but it requires 
a concave glass of 2 D. to give the best vision. 
Now, if the slot is rotated to the opposite merid- 
ian, the 105th, we find that a concave glass of 
5.50 D. is required. We have here a case of 
myopia of 2 D. and myopic astigmatism of 3.50 
D. in the 105th meridian. To correct this, we 
prescribe a concave spherical glass of 2 D. com- 
bined with a concave cylinder of 3.50 D., axis of 
cylinder in the 15th meridian. 

Fifth. — Mixed astigmatism with hyperopia pre- 



202 ASTIGMATISM. 

dominating. Here we find, for instance, that the 
vertical meridian requires a convex glass of 3 D 
and the horizontal requires a concave glass of 
1.75 D. This is, then, a case of hyperopia of 3 
D. in the 90th meridian, and myopia of 1.75 D. 
in the 180th meridian. To correct this, we may 
prescribe a double cylinder or a sphero-cylinder. 
If two cylinders are used, the prescription should 
call for a convex cylinder of 3 D., axis in the 
180th meridian, combined with a concave cylinder 
of 1.75 D., axis in the 90th meridian. 

If a sphero-cylinder is employed, the anomaly 
may be corrected by using a spherical convex 
glass of 3 D. This corrects the hyperopia, but 
increases the myopia to 4.75 D., and hence the 
plus 3 D. spherical must be combined with a 
minus cylinder of 4.75 D. with its axis in the 
90th meridian. 

It can also be corrected by using a concave 
spherical glass of 1.75 D. combined with a con- 
vex cylinder of 4.75 D., axis in the 180th merid- 
ian, for in using the minus spherical glass of 1.75 
D. we have increased the hyperopia to 4.75 D.; 
therefore, the convex cylinder must be of this 
strength. 

Sixth. — Mixed astigmatism with myopia pre- 
dominating. We will imagine this to be a case 
where, if the slot is rotated to the 60th meridian, 
vision is ■§-#, and requires a convex glass of 1.75 
D. to gain the highest amount of vision ; and if 
the slot is rotated into the opposite, or 150th 
meridian, vision is i 2 o°o and requires a concave 
glass of 4.25 D. We have here, then, a case of 



ASTIGMATISM. 203 

mixed astigmatism with myopia predominating. 
To correct this we may nse a double cylinder or 
a sphero-cylinder, preferably the latter. Of the 
sphero-cylinder, either a convex spherical glass 
with a concave cylinder, or vice versa, may be 
employed. Hence we prescribe either a concave 
spherical glass of 4.25 D. combined with a con- 
vex cylinder of 6.00 D., axis in the 150th merid- 
ian; or a convex spherical of 1.75 D. combined 
with a concave cylinder of 6.00 D. , axis in the 
60th meridian. 

If the double cylinder is used, we employ a 
convex cylinder of 1.75 D., axis in the 150th 
meridian, combined with a concave cylinder of 
4.25 D., axis in the 60th meridian. You notice 
here that the axis of the cylinder is always 
placed in the meridian which we do not wish to 
affect by the glass. 

Astigmatism is frequently concealed by the 
power of accommodation, especially in the low 
degrees. In these individual cases, as before said, 
complete mydriasis is imperative that the true 
conditions be revealed; and it is these special 
cases which are so troublesome, the treatment 
oftentimes being unsatisfactory, giving little or 
no permanent relief, the asthenopia persisting. 
Especially are these low forms of astigmatism 
associated with heterophoria, the insufficiency of 
the extrinsic ocular muscles being as responsible 
for the persistent asthenopia as the errors of 
refraction. In treatment the entire amount of astig- 
matism should be corrected and no deduction m^de. 

In prescribing glasses for mixed astigmatism, 
the bi-cylinders give a broader and flatter field; 



204 



ASTIGMATISM. 



and in a high- degree this form of glass is 
considered preferable to the sphero-cylinder. I 
have found in some low cases of mixed astigmatism 
especially in the young, that if I corrected both 
meridians, the glasses were not worn with com- 
fort and satisfaction, but if two pairs were pre- 
scribed — simple cylinders — these were accepted with 
perfect satisfaction; for instance, imagine a case 
of mixed astigmatism of hyperopia of 1.25 D. in 
the 180th meridian, and myopia of J. 75 D. in 
the 90th meridian. Instead of correcting both 
with one glass, I correct the hyperopia with a 
simple plus cylinder with axis in the 90th 
meridian, and the myopia with a minus cylinder, 
axis in the 180th meridian, directing the patient 
to use the former for near and the latter for 
distant objects. 

In case of simple myopic astigmatism, after 
the appearance of presbyopia, instead of using a 
convex spherical and a concave cylindrical glass, 
a convex cylinder only may be prescribed ; as, for 
instance, if we have myopia of 1.50 D. in the 180th 
meridian, and presbyopia of 1.50 D., we may sim- 
ply correct the anomaly by a plus cylinder of 
1.50 D. with the axis in the 180th meridian. The 
cylinder corrects the presbyopia in the 90th 
meridian, and the opposite meridian, previously 
myopic, is now from the presbyopia emmetropic ; 
that is, for near objects. 

Frequently, we find before the use of a mydri- 
atic that the patient will accept a minus cylinder 
varying in amount from 0.25 D. to 1 D. in 
the 180th meridian., but after the use of the myd- 



ASTIGMATISM. 205 

riatic, this concave glass will no longer improve 
vision, bnt a convex cylinder in the 90th merid- 
ian improves. The latter glass reveals the real 
anomaly — simple hyperopic astigmatism. In suck 
a case, the use of the mydriatic has to be con- 
tinued for some time to overcome the spasm ; for 
if not, as soon as the effect of the mydriatic 
passes away, the apparent myopic astigmatism 
will reassert itself. Occasionally, in anisometropia, 
it is found best to correct the eye requiring the 
weakest glass, and then a portion of the ame- 
tropia of the other eye by a glass of the same- 
strength, rather than to correct the full amount 
of each. The former are usually worn with muck 

more comfort and *mmmm* 

satisfaction than the 
latter. In astigma- 
tism, it is especially 
essential that the glasses be properly set, that the 
axis of the cylinder be in the meridian prescribed, 
and that the glasses be so poised as not to allow 
tilting or riding obliquely on the nose, and in 

order to secure this, it 
is best to have them 
mounted in spectacle 
^^— frames rather than in a 
pince-nez. If a pinch-nose is used, the bar frame 
should be employed (Fig. 123) instead of the ordi- 
nary spring (Fig. 124). The glasses should be- 
carefully centered as to the pupils (Fig. 125). 
They should be on a 
plane parallel to that 1 
of the irides, and not 



aiC UOUdllV WUIU ' WILU 111UC1JL 

C i B»mWVinMMQ i >^aia^ 





206 



ASTIGMATISM. 



too far from the eyes, if they are convex and too 
far, the strength is increased ; if they are concave, 
it is diminished. Neither should they be set too 
close to the eyes, lest they touch the lashes. 

In the treatment of astigmatism, some form of 
cylindrical glasses (Fig. 126) must be used. These 
glasses are not kept in stock by spectacle dealers, 
but have to be ground and the axis of the cylin- 
der set in the special meridian for each individ- 
ual case. 

At first, cylindrical glasses 
were ground by hand to meet 
the demand for each individ- 
ual case, and, of course, were 
very expensive ; but more re- 
cently, to meet the great de- 
mand for these glasses, machin- 
ery has been constructed for 
grinding the different forms of 
cylinders with perfect accuracy 
and cheapness, so that the ob- 
jection — expense — in procuring 
these glasses is. largely done away with, and the 
low forms of astigmatism, which are so provocative 
of asthenopia, are now corrected, whereas in 
former days they were ignored, and the patient 
allowed to suffer. 

Cylindrical glasses are in reality sections of 
cylinders instead of spheres, the section being on 
a plane parallel to the axis of the cylinder. Rays 
of light passing through such a glass are refracted 
only in a plane at right angles to the axis of the 
cylinder ; those passing through the axis are 




Fig. 126. 



ASTIGMATISM. 



207 



not changed in their course. Hence, these 
glasses, instead of bringing the rays of light to 
one point as spherical glasses do, refract the rays 




Fig. 127. 



only in one axis, forming a line instead of a point 
(AB, Fig. 127). 

The most common forms of cylindrical glasses 
are the piano-cylindrical convex (A, Fig. 128), 




Fig. 128. 



piano-cylindrical concave (B), sphero-cylindrical 
convex (C), sphero-cylindrical concave (D), and 



208 



ASTIGMATISM. 



crossed cylindrical glasses (E). These latter are 
formed of two piano-cylindrical glasses, the plane 
surfaces placed together with their axes at right 
angles to each other. 

Toricai, Glasses. A torical glass (Latin, 
torus, a tore) is one in which one of the surfaces 
is a segment of an equatorial zone of a tore. 

A tore is a large ring used at the base of a 
column, and whose profile is semi-circular. An 
ordinary rubber ring, such as is given teething 

children to play 
with, will repre- 
sent a tore. If a 
slice be cut off 
from the outside 
of the ring, as 
indicated by the 
HneAB(Fig.l29), 
the convex surface of this represents a convex 
torical glass. A depression into which this sur- 
face will exactly fit represents the surface of a 
concave torical glass. Thus, a plano-torical glass 
has a plane surface, and the other may be convex 
or concave, but the two principal meridians differ 
in their refractive power. A glass, then, with 
one surface torical convex and the other plane, 
acts as a convex glass in the two meridians, but 
stronger in one than in the other, the total effect 
being equal to a convex cylinder combined with 
a convex spherical. The advantage over the cylin- 
drical is that they are more periscopic. Suscipe, 
an optician of Rome, was, perhaps, the first to 
correct astigmatism by means of the torical glass* 




ASTIGMATISM. 209 

With, this glass, the field of vision is supposed to 
be greater and flatter than with the sphero- 
cylindrical. 

Hyperbolical Glasses. In cases of irregular 
astigmatism with slight conicity of the cornea 
(keratoconus), where the curvature is greater in 
the center than towards the border, M. Raehlmann 
has attempted to correct this anomaly by a hyper- 
boloidical glass, but the results obtained have not 
been very satisfactory, because of the irregularity 
of the form of the cornea and the great difficulty 
which presents itself in the construction of the 
glass. For this condition of the eye M. de Wecker 
has constructed a similar glass with the concavity 
increasing on approaching the center. This, too> 
as yet, is of little practical value. 



CHAPTER X. 



ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 



ANISOMETROPIA. 

Anisometropia (&war 9 unequal; juirpoi/^ meas- 
ure; and bftSy vision) is that state in which the 
refraction of the two eyes is unequal, they requir- 
ing glasses of different strength. Any two of the 
several forms of ametropia may exist in the same 
individual. One eye may be emmetropic, the other 
myopic or hyperopic; both may be hyperopic or 
myopic, but of a different degree; one may be 
hyperopic, while the other is myopic ; one may be 
astigmatic, while the other is emmetropic, myopic, 
or hyperopic; again, both may be astigmatic, but 
differing in kind or degree. 

Anisometropia is either congenital or acquired. 
In the majority of cases it is congenital. Acquired 
anisometropia is most frequently brought about by 
extraction of the crystalline leus for cataract. 
Where it is congenital it is attributable to the 
unequal development of the eyes, and may be asso- 
ciated with a simple inequality of the develop- 
ment of the corresponding orbits as well as the 
two halves of the brain. It is frequently asso- 
ciated with asymmetry of the face and cranium, 
yet there may be a marked asymmetry of the 
two sides of the face without any anisometropia. 
The development of the cranium as to its length 

210 



ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 211 

and width influences the development of the shape 
of the eyeballs. 

In anisometropia concurrent with asymmetry 
of the face, Donders has shown that the eye 
with the strongest error of refraction is nearer the 
median line. 

In anisometropia sometimes both eyes fix 
simultaneously, and binocular vision exists. More 
frequently, especially if there is a marked differ- 
ence in the refraction of the two eyes, the anis- 
ometrope uses each eye alternately. In others, 
fixation is limited to one eye, the other being 
allowed to go at will. 

In ^almost every case of error of refraction 
there is a certain amount of anisometropia — in 
appearance, if not in reality; but what appears 
to be anisometropia is often due to a difference 
in the power of accommodation, and not to refrac- 
tion; and when the power of accommodation 
is completely set aside, the vision of both eyes may 
be identical, when the error of the two eyes can be 
corrected by the same kind and strength of glass. 

TREATMENT. 

If one eye is emmetropic and the other ame- 
tropic, it is not advisable, as a rule, to encumber 
the patient with glasses for the sake of trying to 
correct the ametropic eye ; for although the ame- 
tropia may be perfectly corrected, yet this eye with 
the glass and the emmetropic eye will not work 
well together. 

In case of one myopic eye and one hyperopic, 
it is advisable to select the eye with which the 



212 ANISOMKTKUFIA, Ax»HAlt*A, AND PRESBYOPIA. 

patient can work best, correct with, a glass the 
anomaly, and therewith rest content. 

It may be well to advise him, however, of man's 
infinite power to adapt himself to circumstances, 
and suggest that he learn to use the myopic eye 
for near and the hyperopic for distant objects. 
Occasionally, satisfactory results may be gained by 
correcting the anomaly of each eye, giving a con- 
cave glass for one and a convex for the other. 

APHAKIA. 

Aphakia (4, without; and fa/toe, lens) is that 
condition of the eye when deprived of its crystal- 
line lens. 

The crystalline lens, in sztu, has the optical 
action equal to that of a convex lens of 11 D. 
placed in front of the cornea. 

The emmetropic eye deprived of its crystalline 
lens becomes hyperopic to the amount of 11 D. 
If the eye was previously hyperopic, then its 
hyperopia would be increased 11 D.; for example, 
if the eye was previously hyperopic of 2 D. y 
deprived of its lens it would become hyperopic of 
13 D. 

If the eye was previously myopic to the 
amount of 11 D., deprived of its lens it would 
become, theoretically, emmetropic. 

If the myopia is less than 11 D., then the 
eye would be hyperopic to the amount of the 
difference between 11 D. and its myopia. 

If it is more than 11 D., it would be still 
myopic to the amount of the difference between 
the myopia and 11 D. 

Example: If the myopia is 5 D., the amount 



ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 213 

of hyperopia would be 6 D.; if the eye was myopic 
of 12 D., then, theoretically, it would have 1 D. of 
myopia. 

The condition of aphakia may be recognized 
by the following symptoms: Increased depth of 
the anterior chamber with a flattened, tremulous 
iris, and absence of the crystalline reflex in the 
"catoptric test." 

In aphakia the dioptric system of the eye is 
reduced to its simplest form, having the refrac- 
tion of the cornea, aqueous, and vitreous ; the 
two latter, being of the same index of refraction, 
may be considered as one single medium. The 
nodal point of the aphakic eye corresponds with 
the center of the curvature of its cornea, and 
advances when corrected by a strong convex glass 
placed at a certain distance from the cornea; and 
therefore this eye receives a large retinal image. 

The aphakic eye is not only deprived of a con- 
siderable amount of its static refraction, but also 
of its entire dynamic refraction. The power of 
accommodation being gone, two pairs of glasses 
are necessary, one for near and the other for dis- 
tant objects; the stronger for divergent and the 
weaker for parallel rays. This want of accommo- 
dation could be partially supplied by changing 
the position of the glasses with respect to the 
distance from the eye; for the further away the 
convex glass is from the eye (within a certain 
limit) the greater is the amplification ; the hand in 
this instance takes the place of the ciliary mus- 
cle. However, this is only practicable for limited 
distances, two pairs of glasses being absolutely 



214 ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 

necessary, unless it be where the eye approaches 
the emmetropic condition from its previously high 
degree of myopia. 

In the majority of cases of aphakic eyes from 
extraction or absorption of the crystalline lens, 
the glass required for distant objects is about 
-f 10 D., and that for near + 14 D. In the use 
of these strong glasses, a slight variation as to 
position and distance from the eye produces a 
decided change in the refraction. If the glasses 
are tilted from the plane parallel to the iris, they 
produce an effect of astigmatism ; and if they are 
not correctly centered, they will cause very great 
inconvenience in the way of diplopia or displace- 
ment of the object looked at. Astigmatism some- 
times appears after the extraction of the lens, and 
if it is of slight amount, the tilting of the spher- 
ical glass may suffice, correcting the astigmatism 
without the use of cylinders; but if it is of any 
considerable amount, the astigmatism with the 
hyperopia should be corrected by a sphero-cylin- 
drical glass. Unless the glasses are properly cen- 
tered, they act as prisms and displace the image, 
giving a false impression as to height or position ; 
as the floor or steps, making it difficult for the apha- 
kic person to get on or off the cars, or climb stairs. 
This is sometimes true even where the glasses are 
carefully centered, and then can be corrected by n 
periscopic glass, or the combination of prisms. 

PRESBYOPIA. 
As we have already seen, the emmetropic eye 
is not adjusted for near and distant objects at 
one and the same time. It is constantly chang- 



ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 215 

ing in its refraction when viewing objects at an 
infinite distance and when looking at them from 
a finite distance; in other words, the emmetropic 
eye, in its passive condition, is adjusted only for 
parallel rays and has to accommodate itself for 
divergent. This adjustment is brought about by 
the action of the power of accommodation, which 
power is lodged in the ciliary muscle. This 
power, in the emmetropic eye, is adequate to meet 
the demands for about forty or forty-five years, 
when it begins to wane and refuses longer to sup- 
ply this demand, and assistance has to be rendered 
by the use of convex glasses. 

CAUSE. 
From the fact that this power of accommoda- 
tion does not give way until later on in life, and 
vision by the diminution of the power of accom- 
modation is then affected, this condition is called 
presbyopia {yrpea-ftuS) old; and opt?, vision). It is a 
tired and exhausted condition of the ciliary mus- 
cle. This little muscle, which has been con- 
stantly brought into requisition whenever the 
person wished to look from a distant to a near 
object, lasts for forty or more years, but finally 
it gives way completely and refuses longer to per- 
form its function. One, knowing the etymology 
of the word, presbyopia^ is reluctant to acknowl- 
edge this defect, evidencing, as it does, old age 
creeping on. However, this is only true in a 
limited sense, for the hyperope may be presbyopic, 
even at an early age, while the myope is not 
presbyopic until late in life, or, perhaps, never 
becomes so. Presbyopia, then, is a faulty condi- 
tion of the static refraction, demanding relief or 



210 ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 

assistance by the use of a convex glass. At first 
the accommodation only partially gives way, and 
the ciliary muscle asserts its right and refuses to 
be aided except by a weak glass, not tolerating a 
strong one; however, as time advances, the muscle 
becomes more inert and the weak glass has to 
give place to a stronger, until finally the muscle 
ceases almost entirely to act, and a strong convex 
glass is demanded. 

Besides the diminished power of the ciliary 
muscle, the consistency of the lens comes in as a 
factor in presbyopia. The lens, as is well known, 
grows harder from childhood to old age, the hard- 
ness beginning in the nucleus, and the lens loses 
its elasticity. Presbyopia, then, is due to both lack 
of power of the ciliary muscle and diminished 
elasticity of the lens. 

SYMPTOMS. 

In the beginning of presbyopia the person first 
notices the failure of vision when using artificial 
light, as from a lamp ; for although he is able to 
read, perhaps, the finest print by daylight, he has 
to hold the print at a farther distance at night, 
and even then the page may be more blurred and 
the letters indistinct. 

This is one of the first symptoms of presby- 
opia, this desire to get the book or work at a 
greater distance from the eye than has been the 
habit heretofore, since the further away the object, 
the more the rays of light from it approach the 
condition of parallelism, and the less is the demand 
upon the power of accommodation. 



ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 217 

In the emmetropic eye with • presbyopia the 
near point is farther removed, but the far point 
remains at the normal distance; therefore, glasses 
are only required for near objects; however, this 
recession of the near point from its normal posi- 
tion begins really in very early life, about the 
age of ten }^ears, and progresses gradually with 
increasing years. At forty it lies at eight inches, 
and at fifty at eleven or twelve inches. In the 
emmetrope no inconvenience is experienced be- 
fore the age of forty or forty-five years. This 
change in the position of the near point is met 
with in all eyes, whether they are emmetropic, 
hyperopic, or myopic. In the emmetropic at fifty 
there is a slight amount of hyperopia, and at 
seventy or eighty years the hyperopia equals at 
least 0.50 D., and that has to be added to the 
presbyopia. 

DIAGNOSIS. 

An eye is considered to be presbyopic when 
the near point has receded farther than eight 
inches from the eye. The patient then complains 
of work at a near point becoming irksome and 
fatiguing, and asthenopic symptoms appear with 
amblyopia. Although most emmetropic eyes be- 
come presbyopic at the age of forty or forty-five, 
there are exceptions where presbyopia comes on 
at a much later period in life. Prof. Sichel, of 
Paris, called my attention to the fact that he had 
then, at the age of fifty-five, perfect power of 
accommodation, or the absence of presbyopia. He 
was able to read the finest print at the normal 



218 ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 

near point, and yet Had perfect vision for distant 
objects. 

TREATMENT. 

The popular idea of deferring the nse of glasses 
when presbyopia exists is frequently provocative 
of more serious conditions. As soon as the cili- 
ary muscle shows evidence of inability to perform 
its function, it should be aided by the proper con- 
vex glass. Care, however, should be taken not to 
give too strong a glass at first. 

At first it suffices to prescribe glasses for night 
work or for artificial light, allowing the presbyope 
to use his power of accommodation by daylight, 
but after a time it will become necessary for him 
to use a glass at all times when viewing near 
objects. The weakest plus glass that will enable 
the presbyope to read the fine print, No. 1, accord- 
ing to Jaeger, at fourteen inches, indicates the 
glass to be prescribed. 

Each eye should, as in other anomalies, be 
tested separately ; however, it is always best to 
give the same strength of glass to each eye, 
especially if the difference is only slight ; fre- 
quently this difference is dynamic and not static. 
Correct the eye that requires the weaker glass, 
and give the same strength to the other eye. 
However, in exceptional cases of marked difference 
in the refraction of the two eyes, each eye should 
be corrected irrespective of its fellow. 

If there is hyperopia with presbyopia, the glass, 
of necessity, to correct this condition has to be 
sufficiently strong to correct not only the hyper- 
opia, but also the presbyopia. 



ANISOMETROPIA, APHAKIA, AND PRESBYOPIA. 219 

Here, again, glasses of different strength have 
to be used, a weaker for the hyperopia or for dis- 
tant objects, and a stronger for near objects. 

Glasses shonld not be selected in a haphazard 
way by the person himself or by the nntntored 
dealer in spectacles ; more especially by dry goods 
merchants and jewelers. 

The age of a person is not necessarily an index 
of the strength of glass to be prescribed, and the 
"Smart Aleck" who claims to be able to hand ont 
the proper glass once knowing the age is not to 
be trusted. Presbyopia with hyperopia, as we 
have already said, requires a much stronger glass 
than the same aged emmetrope with presbyopia. 
The myope of a slight degree with presbyopia 
would not require so strong a glass as even the 
emmetrope, nor would a spherical glass meet the 
exigencies of the case when there is astigmatism 
combined with the presbyopia. 

Especially is it necessary that the person be- 
ginning the use of glasses have his eyes carefully 
tested by a skilled oculist, and start out with the 
proper glass to meet the exigencies of the case. 



CHAPTER XI. 



HETKROPHORIA. 



INSUFFICIENCY OF THE OCULAR MUSCLES. 



Heterophoria (grepar, other; and fopw, to bear) 
is the term employed to signify that condition of 
the eyes where there is a want of balance of the 
extrinsic ocular muscles due to insufficiency or 
weakness of these muscles. 

Orthophoria (6/)3<h, right) is the term used to 
signify that condition of the eyes where there is 
perfect balance and co-ordination of the extrinsic 
ocular muscles. 

According to Dr. Stevens, orthophoria denotes 
parallelism of the visual lines, or normal power of 
the muscles. 

Heterophoria, non-parallelism of the visual 
lines; or muscular insufficiency. 

Esophoria (%<rtv, within), a convergence of the 
visual lines; or insufficiency of the abductors. 

Exophoria (U<v } without), divergence of the vis- 
ual lines; or insufficiency of the adductors. 

Hyperphoria (u7re'p ) over) is the term used to indi- 
cate that the visual line of one eye is above that 
of its fellow; or insufficiency of the inferior rectus. 

Cataphoria {tcard, down) is the term used to indi- 
cate that the visual line of one eye is below that of 
its fellow; or insufficiency of the superior rectus 



220 




HKTEROPHORIA. 221 

Hyper-esophoria signifies a tending of the vis- 
ual line upward and inward; or insufficiency of 
the inferior and external recti. 

Hyper-exophoria, a tending upward and out- 
ward; or insufficiency of the inferior and internal 
recti. 

Eso-cataphoria, inward and downward; or insuf- 
ficiency of the external and superior recti. 

Exo-cataphoria, outward and downward; or in- 
sufficiency of the internal and superior recti. 

In the four latter 
forms, the oblique mus- 
cles are frequently at 
fault. 

That we may bet- 
ter understand and ap- Figi m 
preciate the anomalies and insufficiencies of the 
ocular muscles, let us briefly consider these 
muscles from an anatomical and physiological 
standpoint. 

Extrinsic Muscles of the Eye. Each eye 
has six muscles, four recti (A, B, C, and D, Fig. 
130) and two oblique (E and F). 

The model (Fig. 131) also represents them. 

The recti originate from the apex of the orbit 
at or near the margin of the optic foramen, and 
surround the optic nerve as it passes into the 
orbit (Fig. 132). They extend forward and are 
inserted into the sclera by their tendinous extrem- 
ities at about five or six millimeters back of the 
limbus. The superior oblique (E) also has its ori- 
gin at the apex of the orbit, but its functional 
attachment is at the anterior, superior, and internal 



222 



HETEROPHORIA. 



portion of the orbit, where it passes over a pulley 
(c, Figs. 130 and 132). 

The external rectus (C) has its attachment a 
little further back on the sclera than the internal 
(D). The superior oblique (E) wraps around the 
upper part of the globe, passing under the supe- 
rior rectus, and is inserted into the sclera at its 
outer side just back of the equator of the eye. 




Fig. 131. 

The inferior oblique (F) takes its origin from the 
anterior and inferior portion of the orbit, wraps 
around the lower portion, going beneath the infe- 
rior rectus, and is inserted into the sclera near the 
insertion of the superior oblique. 

The combined action of the recti is to retract the 
globe into the orbit, while that of the oblique is 
to advance it and also slightly turn the cornea out- 



HETBROPHORIA. 



228 



ward. The superior and inferior recti rotate the 
ball on a vertical plane, while the external and 
internal recti rotate it on a plane transverse to the 
vertical, but with the outer pole of its axis further 
back than the inner because of the external rectus 
being inserted further back than the internal. 




The individual action of the muscles is as fol- 
lows: The superior rectus (A, Figs. 130 and 131) 
rotates the eye upward and slightly inward. The 
inferior rectus (B) rotates it downward and slightly 
inward. The external rectus (C) moves the eye 
outward and slightly upward or downward, accord- 
ing to the way the eye is directed. The internal 
rectus (D) turns the eye inward and, beyond a given 
point, slightly upward or downward. The superior 
oblique (E) rotates the eye slightly downward and 
outward, while the inferior oblique (F) rotates it 
upward and outward. 



224 HETEROPHOKIA. 

In order to have perfect balance and co-ordina- 
tion, each muscle must have its quota of strength, 
one antagonizing or balancing the other; and 
when certain movements are made, one predomi- 
nates over the other. 

The muscles are supplied by the third, fourth, 
and sixth pairs of nerves. 'Three of the recti (supe- 
rior, inferior, and internal), and the inferior oblique 
are supplied by the oculo-motor, or third; the supe- 
rior oblique by the trochlearis, or fourth; the exter- 
nal rectus by the abducens, or sixth. 

The adductors are the internal recti, assisted by 
the superior and inferior recti, and antagonized by 
the abductors. 

The abductors are the external recti and the 
oblique, antagonized by the adductors. 

The muscles that direct the eye upward are the 
superior rectus, inferior oblique, and upper fibres 
of the external and internal recti, antagonized by 
those that direct it downward. 

The muscles that direct the eye downward are 
the inferior rectus, superior oblique, and lower 
fibres of the internal and external recti, antago- 
nized by those that direct the eye upward. 

In looking obliquely upward and outward, there 
is a combination of the superior and external recti 
with the inferior oblique; downward and outward, 
the external and inferior recti with the superior 
oblique ; inward and upward, the superior and inter- 
nal recti; downward and inward, the internal and 
inferior recti. 

The rotary motion is effected mostly by the 
oblique, although the recti assist alternately. 



HETEROPHORIA. 225 

Ordinarily, we fix our vision on near objects, 
thus converging the optic axes, and so bring the 
adductors more constantly into action. By this fre- 
quent use of the adductors a preponderance of 
power over the abductors is gained. In the 
emmetropic eye the adductors can overcome a 
prism of 16° or 20° with the base outward, while 
the abductors can only overcome a prism of 3° to 
6° with base inward. In looking off at a distance, 
there is a demand upon the abductors. 

The imaginary line drawn from the macula 
lutea through the nodal point to the object looked 
at is called the visual line, and the place where 
the visual lines of the two eyes meet is called the 
point of fixation. 

Horopter. The horopter (8/>or, a boundary; 
d7rTj}/3y one who sees) is that region of external space 
the different points of which are imaged on the 
maculae or corresponding spots of the two reti- 
nae, thus one exactly covering the other; or, in 
other words, it is that space within which both eyes 
can fix the object at one and the same time. If 
the face is directed toward a certain object, the 
two eyes may fix this object simultaneously with- 
out difficulty; also all objects, without changing the 
position of the face and within a certain limit, are 
seen simultaneously with both eyes, and binocular 
vision is maintained ; but beyond a certain limit 
one eye may fix the object while the other lags, 
and the image of the object falls to one side of 
the yellow spot and diplopia — double vision — is 
the result. This space, then, in which any and all 



226 HETEROPHORIA. 

objects may be fixed by both eyes simultaneously, 

is called the horopter. 

The horopter varies in its scope in different 

individuals. In some it is much larger than in 

others and is greater in certain directions. 

CAUSE. 
In order that binocular vision be enjoyed, both 

eyes must fix the object at one and the same time; 
that is, the image must fall upon the macula of 
each eye, or, if outside of the macula, the location 
of one must exactly correspond with that of the 
other. For all objects on which we do not fix the 
fovea are away from the line of direct vision, and for 
them we have diplopia; but we are not disturbed 
by double vision of an object upon which we are 
not fixing attention ; we ignore such objects : as 
an illustration, we work with the microscope or 
view the fundus of the eye with the ophthalmo- 
scope with both eyes open, ignoring the objects 
seen by the eye unemployed. 

If there is a lack of balance of the muscles due 
to insufficiency, or preponderance of power on the 
part of one muscle or set of muscles, co-ordination 
is imperfect, and it is with constant effort that 
binocular vision is maintained. One eye deviating, 
the images of the objects do not impinge at cor- 
responding places ou the retinae ; therefore, one 
image does not exactly cover the other, but laps 
on to the other, or they are entirely separated, and 
partial or complete diplopia results; or, if binocu- 
lar vision is maintained, it is with the greatest 
effort, taxing to the utmost the power of co-ordina- 
tion, with a strained, tired feeling of the eyes 
resulting. 



HETEROPHORIA. 227 

Insufficiency of these muscles may be due to 
enervation and is frequently found in persons of 
delicate health, who are weak, nervous, debilitated, 
and overworked. It may be as a reflex from some 
uterine disease or affection of any of the genital 
organs, disease of the rectum, of the lachrymal ap- 
paratus, hypertrophy of the turbinates, nasal polypi, 
enlarged tonsils, etc. It is most frequently due to 
some anomaly of refraction — hyperopia, myopia, or 
astigmatism. Very frequently it is associated with 
anisometropia. There should always be a certain 
reserve force of the muscles or static power to 
insure indemnity against asthenopia (weak sight). 
As yet, the exact amount is not determined.* This 
insufficiency of the ocular muscles or so-called 
heterophoria may be due to a congenital insuffi- 
cient amount of fibres in one or more of the mus- 
cles; to an abnormal attachment or position of the 
tendon of the muscles, either too far back or too 
far forward or obliquely attached; or it may be 
due to an abnormality as to the position of the 
yellow spot of one eye; or it may be due to an 
enervation or congenital lack of nerve supply. 
That it is usually dependent upon some form 
of ametropia is generally conceded; however, it is 
frequently found in a perfectly emmetropic eye. 
Weakness of the adductors appears with myopia 
and myopic astigmatism. Weakness of abductors 
appears with emmetropia, hyperopia, and hyper- 
opic astigmatism. 

This static or latent reserve force can be esti- 
mated by the use of prisms; as, for instance, if a 
weak prism is placed before one eye with base 

*The dynamics of the recti muscles, as obtained by the examination of 100 sol- 
diers, conducted by Dr. Banister, of Fort I^eavenworth, and of 100 medical students, 
made by myself, showed the average abduction to be 8°-6°; adduction 16°-20°; sur- 
sumduction, l°-2°; deorsumduction, l°-2°. 



228 



HETEROPHORIA. 



inward (Fig. 133) and we look at an object, as a gas- 
jet; the jet may appear donble at first and then the 
two jets approach each other and finally fuse. At 
the same time, the eye with the prism before it is 
seen to move outward; this turns the base of the 
eye inward so that the image of the jet which 
the prism has deflected inward may fall upon the 
macula lutea. By placing the prism base outward 
(Fig. 134), the adductors may be similarly tested. 
The power of abduction is much less than that of 
adduction ; for whereas the abductors with the base 
of the prism turned towards the nose can only, as 
a rule, overcome from three to six degrees, the 
A a. 




Fig. 133. Fig. 134. 

O, Fixation Point; S, Impinging Point; M, Macula IyUtea; C, Center of Eyeball; 
A, Place of Projected Image; OM, Visual Line; CS, Radius of Curvature. 

adductors will overcome a prism of from eight to 
twenty degrees ; that is to say, with a prism of a high 
degree, base outward, deflecting the image towards 
the temple, the eye will turn sufficiently inward 
to throw its base outward that the image may 
impinge upon the macula. 

As has been said, we cannot at the present 
time state just how much latent power is neces- 
sary to insure indemnity against the functional 



HETEROPHORIA. 229 

muscular insufficiency called " muscular astheno- 
pia." What would constitute a normal condition 
in one person might be an insufficiency in an- 
other. 

Insufficiency of the externi is much more fre- 
quent than of the interni. As already said, in- 
sufficiency usually co-exists with some error of 
refraction. Yet not infrequently is it present in 
a perfectly emmetropic eye, or in eyes with very 
slight ametropia. 

Dr. Noyes finds in one hundred cases of heter- 
ophoria, treated within two years, from 3885 to 
1887: 

INSUFFICIENCY OF EXTERNAL RECTUS. 

Emmetropic 45 

Hyperopic , 9 

Myopic .... 1 

Hyperopic astigmatism 13 

Myopic astigmatism 4 

Mixed astigmatism 2 

Total ~U 

People beyond the age of puberty are more 
susceptible to heterophoria than those under ; yet 
many children from seven to fifteen have it, and 
even to that extent that requires operative pro- 
cedure. 

SYMPTOMS. 
Insufficiency of the ocular muscles — hetero- 
phoria — simulates certain nervous conditions mani- 
fested in neurasthenic people with active mental 
faculties. Hundreds have this anomaly and do 
not know it. It is called "frontal" or " temporal 
headache." People thus affected complain of be- 
ing unable to read long at a time without tht 



230 



HETEROPHORi, 



eyes tiring, aching in the depth of the eyeball, 
a dizziness and swimming sensation, and inability 
to appreciate distances. In aggravated cases the 
floor or ground seems uneven ; climbing stairs is 
done with difficulty ; there is vertigo, especially 
when looking from a great elevation. Objects 
may or may not appear double ; if not, they may 
be slightly shaded or fringed at the edge,; or the 
double images may constantly separate and ap- 
proach or even fuse, and, for a time, be one. 




Fig. 135. Fig. 136. 

O, Fixation Point ; S, Impinging Point ; M, Macula Lutea ; C, Center of Eyeball ; 
A, Place of Projected Image ; OM, Visual Line; XM, Optic Axis; CS, Radius of 
Curvature. 

There is a constant effort to co-ordinate, and 
this effort brings on nausea (sick headache, so 
called) and dizziness. Life becomes a burden ; 
despondency, melancholia, insomnia, insanity, and 
suicide may be the end. If the abductors are at 
fault, the eye turns inward, throwing the fundus 
outward, and the image is mirrored upon the 
retina inside of the yellow spot, and is projected 
outward (SA, Fig. 135), producing homonymous 
diplopia; that is, the left image is seen by the. 
left eye, and the right by the right e\^e. 



HETEROPHORIA. 231 

Where the adductors are at fault, the eye devi- 
ates outward and the false image is thrown across; 
for here, the eye turning outward, the fundus 
turns inward, and the image is mirrored upon the 
retina outside the yellow spot, and is projected 
across, thus giving rise to heteronymous or 
crossed diplopia (Fig. 136). Here the left image 
is seen by the right eye, and the right by the 
left. 

In the first place we have convergence of tne 
axes, and in the other, divergence ; but it is fre- 
quently the case that the inferior or superior 
recti or the oblique may be at fault, and one 
image be directly or obliquely above the other. 

Asthenopia, as we have said, may depend upon 
various causes. If upon refractive errors, it is 
then brought about by overtaxing the power of 
accommodation (the ciliary muscle), as well as 
by insufficiency of the external ocular muscles. 
However, .as said, an emmetropic eye, with abso- 
lutely no anomaly of refraction, becomes asthen- 
opic from neurasthenia and reflex troubles, as 
catarrh of the nasal and post-nasal passages ; for 
there is an intimate connection between affections 
of the eye and those of the lachrymal apparatus, 
as well as those of the nasal passages and frontal 
sinuses, one depending upon or influencing the 
other. 

All forms of uterine disease are liable to pro- 
duce asthenopia. Overwork, sewing, reading, 
writing, engraving, or reading while lying down, 
or on the moving car, or carriage, may produce 
asthenopia. While in a recumbent position, un 



^2 HETEROPHORIA. 

less the paper or book be held directly above the 
face, there is a constant strain npon the inferior 
recti muscles, in order to turn the eyes sufficiently 
downward upon the page. This soon results in 
fatigue to these muscles. In reading in a jostling 
car or carriage the power of accommodation is 
brought into excessive requisition, and so the 
ciliary muscle becomes tired and ciliary neuralgia 
or frontal or temporal headache results. 

SYMPTOMS. 
There is pain on using the eyes for near 
objects, especially in hyperopia, where the power 
of accommodation and the muscles of adduction 
are constantly called into use ; for the nerves that 
supply the power of accommodation and that of 
adduction have the same origin or are intimately 
connected. Many people also experience much 
pain in looking at distant objects, as in the 
church or the theater. Especially is this the case 
when there is a slight myopia with insufficiency 
of the adductors, and people thus affected will 
complain of a blur or cloudiness or a slight halo 
or shade about, or at one side of the object looked 
at. Occasionally they will complain of double 
vision. It is in these cases of slight amount of 
error of refraction and muscular insufficiency that 
the symptoms are most pronounced, for the images 
are so near together, now blending, again sepa- 
rating or passing off to one side or the other, 
that great confusion and suffering arise with a 
constant strain and effort to co-ordinate. Medi- 
cines do not help ; glasses do not help ; rest does 
not help — it seems that there is no help. These 



HETKROPHORIA. 233 

are the cases that require the most careful atten- 
tion and searching examination. 

The power of accommodation must be com- 
pletely set aside by a strong mydriatic, repeated 
and continued for several days, in order that 
any hidden ametropia, however slight, may be 
revealed and corrected. Any insufficiency of the 
recti or oblique muscles must also be corrected. 
This correction is frequently brought about by 
enjoining rest, toning up the system, or by slight 
gymnastic exercise of these muscles by means of 
prisms. Others may require either a graduated or 
complete tenotomy. 

These different forms of heterophoria are 
among the most perplexing and obstinate affec- 
tions the oculist has to deal with, and unless the 
greatest care, patience, and skill are exercised in 
ferreting out the real anomalies and the exact 
treatment prescribed, all is to no purpose, all is 
confusion and no relief is given. The pain is usu- 
ally referred to the ball itself, sometimes to the 
temples, over the brow, or to the base of the 
brain, and frequently ends in nausea, sick head- 
ache, and vomiting. In neurotic and feeble 
patients, the muscular errors or insufficiencies may 
produce aphonia, diarrhoea, pain of the ovaries, diz- 
ziness, St. Virus's dance, and insanity even. Asthe- 
nopia and hysteria frequently go hand in hand. 
There is no doubt that epilepsy is frequently due 
to some insufficiency or anomaly of some of the 
muscles of the eye ; to want of balance, especially 
if these insufficiencies are associated with hyper- 
opia or astigmatism. 



234 HETEROPHORIA. 

Dr. Stevens cites man}' cases of epilepsy cured 
by tenotomy of the recti. Dr. Ranney also speaks 
of many cases of epilepsy and of mania cured by 
restoring trie balance of the ocular muscles, either 
by surgical aid or by use of prisms; in other 
words, by curing the heterophoria. 

If the two eyes are caused to move in certain 
directions for a given distance, they may move in 
harmony and perfect co-ordination and balance 
may be maintained, but beyond this point one 
will waver, for its excursive capability is limited; 
the axes no longer maintain parallelism- and the 
patient complains of seeing the object looked at 
as double. This may be true when looking in 
certain directions, or in all directions if past a 
certain distance from the median line. The power 
of abduction should not fall below three or four 
degrees. That is to say, a prism of 3° or 4° with 
base placed towards the nose, refracting the rays 
inward, should be overcome by the abductor. 

So also should the adductors overcome a prism 
of 18° or 20° with base outward. Of course, ex- 
ceptional cases exist, where the muscular power 
is much below this, with a perfect balance and 
no asthenopia. 

As above said, these anomalies frequently exist 
unknown to the patient, and without careful and 
most searching examination with the various 
tests now known they will be overlooked even by 
the oculist. The physician not giving especial 
attention to such affections is at a loss to account 
for the persistency of pain, inability to read long 



HETEROPHORIA. 



235 



at a time, vertigo, headache, and many other 
symptoms. 

In his vain effort to account for the trouble, 
he seeks its etiology in malaria, biliousness, liver 
disorder, gastric, uterine, or mental disturbances. 

How to Test the Strength of the Mus- 
cles and Detect any Existing Insufficiency 
Thereof. First, correct any existing ametropia. 
Place before the right eye a prism of 3° or 5° 
with base in the vertical, say upward, and have the 
patient look at a distant object. This prism will 
cause vertical diplopia, for the superior or inferior 
recti are capable of overcoming only a very low 
amount, say two or three degrees. If the two 
images are exactly one above the other, both be- 
ing in the vertical line without any muscular 
effort, there is no insufficiency of either the in- 
ternal or the external recti; or, in other words, 
the adductors and the abductors balance; but if 
the lower image — the one seen by the right eye — 
deviates to the right, we have homonymous diplopia 
from weakness of the abductors (esophoria). If 
this lower image goes to the left, we have heteron- 
ymous or crossed diplopia, due to insufficiency of 
the adductors {exophoria). In the first instance, 
the prism, with base outward, that will bring the 
two images into the vertical line will indicate the 
amount of esophoria. In the second instance, the 
prism, with base inward, that will bring the two 
images into the vertical line will show the amount 
of exophoria. 

There are several tests for detecting hetero- 
phoria. If examining for near objects, we may 



236 HETEROPHORIA. 

select the vertical line test and see if there is per- 
fect equilibrium of the abductors and adductors. 
Employ a weak prism, say three to four degrees, 
with base vertically upward. The prism is placed 
in trial frames before, say, the right eye. The 
patient is then asked to look at a fine line with 
a dot in its center (Fig. 137) at a distance of 
twelve or fourteen inches from the eye. The prism 
has produced vertical diplopia. There are two 
images of the dot, one above the other, varying in 
distance according to the strength of the prism 
and the distance at which the line is held from 
the eye. If the two dots are in the 
vertical line, one exactly above the other 
(Fig. 138), there is perfect balance of 
the abductors and adductors. Fre- 
quently there is some wavering of the 
images, due to a slight weakness, which 
should not be accredited as a form of 
Fig.137. Fig. 138. heterophoria; but if it exceeds four or 
five degrees, it should be so regarded. 

If the deviation is that of convergence, it shows 
a defectiveness of the abductors; for instance, with 
a prism placed with its base upward before the 
right eye, the rays passing through the prism 
will be bent toward the base and will impinge 
upon the retina above the yellow spot, and the 
image will be projected down. Now, if this im- 
age fall upon the vertical line exactly below the 
other, there is perfect balance of the abductor 
and adductor muscles; but if it goes to the right 
and below, it indicates convergence of the eye or 
insufficiency of the abductors , for here the im- 



HRTEROPHORIA. 237 

age impinges upon the retina inside the yellow spot, 
and is projected outward, suggesting weakness of 
the external rectus ; but, as before said, if it be 
but a slight amount, it need not be considered an 
abnormality. If the lower image is thrown across 
to the left, it indicates divergence of the axes, or 
insufficiency of the adductors; for here the image 
impinges upon the retina outside of the yellow 
spot and is projected across ; hence, a weakness of 
the internal recti or adductors. Now the prism 
that will correct these deviations and bring the 
image exactly upon the vertical line will show the 
amount of esophoria or exophoria, as the case 
may be. ' 

In examination for heterophoria we should 
test the eyes for both near and remote objects, as 
there are many different forms and combinations. 
A muscle or set of muscles may be normal in 
function for near objects, but for remote objects 
may be insufficient, and vice versa. Again, there 
may be a defect for both remote and near objects. 

Not infrequently do we find a defective adduc- 
tion both for near and distant objects, indicating 
an insufficiency of the interni; or defective abduc- 
tion for remote and near objects, indicating faulty 
externi. Defective adduction for near but not for 
distant objects occasionally exists. 

Defective abduction greater for working than 
for distant point is also found. 

Defective abduction for distant and defective 
adduction for the working point — i. e., insufficiency 
of externi for distant and of interni for near 
objects — is occasionally met with. (In this last con- 



238 



HETEROPHORIA. 




dition we should have homonymous diplopia for 
distant objects, "but heteronymous or crossed di- 
plopia for near objects. ) In other cases we may 
have a debility or insufficiency of all the different 
muscles and for all distances, showing a general 
weakness. 

Maddox has given us several most valuable 
tests for ascertaining these heretofore occult and 

troublesome affections. If 
we go through a fixed and 
settled form of revealing 
the different kinds of mus- 
cular insufficiencies, we shall 
then be in a better position 
to correct the same. 

Maddox Rod Test. This 
instrument consists of a glass 
rod set in an opening of a metal disc (Fig. 139). 
The rod should be placed in the anterior recepta- 
cle of the spectacle frame (the posterior receptacle 
holding the glass to correct any existing error of 
refraction). The glass rod acts as a 
strong cylindrical lens and causes the 
candle flame or gas light looked at to 
appear as a long streak of light. If the 
superior and inferior recti of the right 
eve are to be examined, the rod is 
placed vertically before this eye and 
the patient requested to look at a can- 
dle flame or gas light, with both eyes, at a distance 
of eighteen or twenty feet. The gas flame or jet is 
seen distinctly with the left, while with the right 
eye a long streak is seen extending horizontally. 



Fig. 139. 



i. 1 1 una c 



' — ~ 



2 



a a 



J= 



b 



HETEROPHORIA. 



239 



Now, it is the left eye that fixes the flame, and if 
there be orthophoria, the streak will pass through 
the flame as is represented in Figure 140 (a). 
If there be hyperphoria, the streak will be below 
(b). If there be cataphoria, it will be above (c). 
The amount of heterophoria is indicated by the 
strength of the prism, placed before the eye, that 
will throw the streak into the normal position; 
viz , position a y Fig. 140. If hyper- 
phoria be found in one eye, the other 
eye tested in the same way shows 
the same degree of cataphoria. 

To test the adductors and abduct- 
ors, the rod must be placed before the 
eye in the horizontal meridian. The 
streak will then appear vertically. 
If we first test the right eye, the gas 
jet at twenty feet will be distinctly 
seen by the left, while with the right 
a light streak will be seen in the 
vertical direction. 

If there is perfect orthophoria, the 
streak will pass directly through the 
represented in a (Fig. 141). If there be esophoria, 
the streak will be to the right (<$); if exophoria, 
it will be to the left (c). Each eye being tested, 
it will be found that if there be esophoria of the 
right, there will also be esophoria of the left; and 
if there be exophoria of the right, there will be 
the same form in the left and of the same degree; 
the amount of which can readily be ascertained by 
the prism, placed before the eye, that will throw 
the light streak into the flame, as represented by a. 




Fig. 141. 



flame, as is 



240 



HETEROPHORIA. 



Maddox Has another test which shows any com- 
pound muscular error, as it will indicate at once 
any defect of the vertical with that of the hori- 
zontal as well as the oblique muscles. This is 
his double prism test, consisting of two prisms set 
in a rim (Fig. 142) with bases together, having the 
effect of doubling objects. This is placed in the 
frame before, say the right eye, the left being cov- 
ered by an opaque disc. 
The candle, door-knob, or 
object looked at, at twenty 
feet, will appear double if 
the base line of the prisms 
cuts the center of the pupil. 
The images of the object 
— the door-knob — will be 
separated to the distance 
inches, one being directly 
Now, if the 




Fig 142. 



of twelve or fourteen 

above the other, as in Figure 143 a 



O 



O 






o 
































i 




c 

Fig. 


143 




d 




e 




/ 



left eye is uncovered by removal of the opaque 
disc, another image will be seen between the two, 
and if there be orthophoria, the third will be ex- 
actly in the vertical line with the other two and 
midway, as is represented by b. But if the mid- 
dle figure goes to the left (V), this indicates eso- 
phoria. If it goes to the right, it shows exophoria 
(d). Going nearer the lower figure indicates 
hyperphoria of the left eye (e). Going nearer the 
upper indicates left cataphoria {/). In the same 



HKTEROPHORIA. 241 

way, of course, the right eye may be tested and 
the degree of heterophoria ascertained by the 
strength of the prism required to throw the single 
image into its normal position; viz., in the vertical 
line midway between the other two (d). This 
double prism test can also be used in testing the 
muscles at a near point, as is beautifully shown by 
Dr. Savage, by using the Von Graefe line and dot 
test, First, place the double prism in the frame 



Fig. 144. 



before the right eye, covering the left with an 
opaque disc ; then have the patient look at the line 
with dot (Figure 144, a), changing the position of 
the head, upward or downward, until the line and 
dot are seen as double (Figure 144, b). Now, if the 
left eye is uncovered, a third line will be seen, and 
if orthophoria exists, the third line will be mid- 
way between the other two, and its dot exactly in 

the vertical line with the other two dots (c). But, 
1 t 



Fig. 145. 

if there is esophoria, the middle dot will be to the 
left (Fig. 145, a). If there be exophoria, it will be 
to the right (5). If there be hyperphoria, it will 
be nearer the lower (Fig. 146, a). If there be 
cataphoria, it will go nearer the upper (6). If there 

be hyper-esophoria, the • • 

middle line will go to 5 , 9 

the left and below (Fig. a Fig . 146 . 

1,47, a). If there be hyper-exophoria, it will go to 



242 



HETEROPHORIA. 



the right and below (6). If there be eso-cataphoria, 

• • it will go to 

* ~ — - 9 ^sz the upper and 

left (Fig. 148, 

Fig. 147. a). If there be 

exo-cataphoria, it will go to the upper and right (5). 

The following method is a very simple and 

speedy test or mode of 

detecting any insuffi- • • 

ciency of the abduc- * f 

tors or adductors. It Fig - m 

is with a card of double letters, A-B-C-D-E, one 
set red and the other black, separated by an arrow, 
shown in Figure 149. Place the card at twenty 
feet, then test either eye with a prism of 4°, say 



i 



I I I 



M i I I M i I i I I 



DCBA . ABODE 
T 

(Black) (Red) 

Fig. 149. 



base down. The prism doubles the image and the 
person tested sees two cards, the false one being 
above, as shown in Figure 150. 

If there is perfect balance, or orthophoria, the 
arrow of the false or upper card will point to the 
arrow of the lower card. But if there is esophoria, 
the arrow will go to the right (the right eye being 
the one tested), and if there is exophoria, it will 
go to the left. 

As the space between each letter indicates 1°, 
the amount of insufficiency can be easily read off. 
As, for instance, if the arrow points to the letter 
A to the right (Figure 150), it would indicate I 9 



HKTKROPHORIA. 243 

of esophoria, showing an insufficiency of the abduc- 
tors; if the arrow moves to the left and points to 
the letter A, it shows insufficiency of the adduc- 
tors, or heteronymous diplopia, or exophoria to the 
amount of 1°. 

Dr. Spencer has combined this with Stevens' 
phorometer, making a good test (Figs. 151 and 

vvv\ ] \ ri'iTj 

SDCBA . ABODE 

▼ 

(Black) (Red) 




IMT 

ABCSfi 



(Black) (Red) 

Fig. 150. 

152). Stevens' phorometer is a scientific and 
accurate instrument. I give the following descrip- 
tion as furnished by Meyrowitz Bros., the manu- 
facturers, taken from their catalogue, pages 40 and 
41: 

"The instrument consists of the standard A 
supported by a tripod. The standard is freely 
extensible, permitting a ready adjustment for differ- 
ent statures of patients. The arm B is grooved 
and allows the prism carrier C to rest securely, to 
slide freely from end to end of the arm, or to be 
removed at will. At E a spirit level is attached 
to the arm, by means of which the horizontal posi- 
tion of the arm can be determined. The semi- 
circular piece of the head of the arm is spirally 



244 



HETEROPHORIA. 



toothed and is acted upon by the endless screw at 
F, which imparts to the arm an upward and down- 
ward elbow movement. The semi-circle is gradu- 
ated in degrees, and a fine pointer indicates the 
extent of motion imparted by the screw. By means 




of the lever G the 
screw can be un- 
locked, allowing 
the arm to fall to 
the side of the 
standard. 

"The slide (C) 
contains two cells, 
in each of which 
rotates a disc, each 
disc carrying a 
prism of 5°. Each 

disc is furnished with a border of teeth or cogs. 

A small gear-wheel placed between the two discs 




Fig. 151. 



HETEROPHORIA. 



245 




Fig. 152. 



communicates the movements from one disc to 
another. Around the outer part of the border of 
each cell is a narrow raised band on which is 
marked a scale of degrees, increasing from the cen- 
ter each way from 0° lU^lI 
to 8°, the number rep- f^SSSl 1 *3 ■ « 
resenting the refract- 
ing angle of prism — 
the method of notation 
now commonly used. 
A second scale just out- 
side the first is simi- 
larly graduated, accord- 
ing to the new system 
of designating prisms by the refracting power or 
number of degrees of minimum deviation." 

Directions. — To determine hyperphoria, bring 
the lever of the prism slide to the vertical position, 
the pointer being at zero. The patient, looking 
through the glasses at a lighted candle twenty feet 
away, sees a double image of the candle. Should 
one of the images appear higher than the other, the 
prisms are caused to rotate until the images are 
brought to the same horizontal plane. The pointer 
then indicates the kind and amount of manifest 
hyperphoria. 

To examine for esophoria and exophoria, bring 
the lever to a horizontal position and then make 
adjustments until the images are in an exact ver- 
tical line. 

The supplemental prisms must be used with 
base in if the prisms in the instrument are not 
sufficiently strong to cause diplopia. If the prisms 



246 



HETEROPHORIA. 



in the instrument are so strong as to widely sepa- 
rate the images, the supplemental prism should 
be placed with the base out. 

The accompanying cut represents Prince's phor- 
ometer, which is a convenient and reliable test for 
ascertaining the strength of the extrinsic ocular 
muscles, and is cheaper than Stevens's ; however, we 
have found from actual practice that Maddox's 
double prism and rod tests (Figs. 130-142) take the 

place of these more ex- 
pensive and complicated 
phorometers, are more eas- 
ily applied, and are just as 
reliable and accurate in 
their revelation ; in fact, 
they are even better for 
the examination and test- 
ing of the ocular muscles 
for both near and distant 
objects. 




TREATMENT. 



Refractive errors are to be first looked for, and 
if any exist, they must be accurately corrected, giv- 
ing, as a rule, a full correction; especially is it 
necessary in hypermetropia when it is associated 
with esophoria, but if it is associated with exo- 
phoria only a partial correction should be made; on 
the other hand, in myopia with exophoria the full 
correction should be given, but only a partial cor- 
rection when it is associated with esophoria. Hav- 



HETEROPHORIA. 247 

ing ascertained the amount of heterophoria, if it be 
on the operative line, as indicated by Dr. Savage, 
then the kind of operation is to be determined, 
whether it be complete tenotomy or partial (grad- 
uated tenotomy, so called). If the heterophoria is 
of a low degree, all means should first be used to 
correct it without an operation. Frequently a slight 
heterophoria can be corrected by decentering the 
glasses required for the correction of the error of 
refraction; for, as is well known, either a convex 
or concave glass looked through excentrically acts 
as a simple prism. Muscular asthenopia without 
any error of refraction exists far more often than 
was formerly thought, and it is these cases that 
have so perplexed the general practitioner and 
even "stumped" the oculist. It is in these cases 
that we derive special benefit from the gymnastic 
exercises with prisms. Occasonally, partial tenot- 
omy has to be made; but it is a rare case indeed 
that demands complete severing of the tendon. It 
is much better to under-correct and have to repeat 
the operation than over-correct and be obliged to 
advance the opposing muscle. In making gradu- 
ated tenotomy, the outer fibres above and below 
or the central fibres may be severed. Of course 
if there is mixed heterophoria, say hyper-esophoria, 
then the upper fibres should be the ones severed. 
Ordinarily, the central fibres are the ones to be 
selected. The operation should be made under the 
influence of an anaesthetic of cocaine of 4 per cent. 
The incision should be directly through the con- 
junctiva; the tendon is grasped by means of a 
delicate rat-toothed forceps near its insertion, and 



248 HETEROPHORIA. 

with, delicate, blunt, slightly curved scissors the 
fibres are severed close to their scleral attachment. 

The eyes should be immediately tested to ascer- 
tain if the correction is sufficient. Besides the 
correcting of the heterophoria by glasses and by 
operation, other measures must be used. In the 
first place, the patient's general health should be 
looked after; he must be supported by tonics, by 
good food, and hygienic surroundings; rest from all 
work with the eyes for a time should be enjoined, 
proper exercise, horse-back riding, gymnastics in 
the open air judiciously directed, massage, Turkish 
bath, etc. Often the muscles may be strengthened 
by a course of gymnastics with prisms. It is best 
to have the patient visit the office daily and wear 
a prism of a certain degree before each eye, say 
for an hour or so, increasing the strength from 
day to day. First wear base inward and then out- 
ward. If it is desirable to strengthen the supe- 
rior or inferior recti, a weak prism with its base 
upward or downward may be employed as in exer- 
cising the adductors and abductors. In this way 
the strength of the muscles can be augmented. 
Care should be taken not to give too strong a 
prism at first, nor should the prisms be worn too 
long at a time. It is sometimes a good plan for 
the patient to use the eyes for near work a cer- 
tain length of time every day. 

Dr. Savage has suggested a plan of gymnastic 
exercise with prisms which I have adopted and 
found to give satisfactory results. Dr. Savage 
calls it the " Rhythmic Exercise with Prisms." 
In giving this exercise, place a weak prism before 



HETEROPHORIA. 249 

each eye, sufficient to produce diplopia, yet not 
so strong but with a little effort they can be 
overcome and the two images fused. As soon as 
the images run together, the patient raises the 
prisms, when, for an instant, he sees double ; and as 
soon as the images are again fused the prisms 
are dropped before the eyes, when the patient 
again sees double, but only for an instant, as the 
two images will immediately shoot one into the 
other. Then the prisms are again lifted, and so 
this rhythmical exercise is continued for a few 
moments, thus exercising the muscles of the eye 
and augmenting their strength. By placing the 
bases in different directions, any one or set of 
muscles may be thus exercised and strengthened. 
Static electricity applied to the eye-ball and up 
and down the spine three to five minutes daily I 
have found to give relief and to be of permanent 
benefit. 

How to Detect and Correct Insufficiency 
of the Oblique Muscles According to Savage. 
" Place a double prism (Maddox's prism) before one 
eye, the other, for a moment, being covered with 
an opaque disc. Ask the patient to look at a hori- 
zontal line on a card held 18 inches away. The 
effect of the double prism is to make the line 
appear as two, each parallel with the other. The 
other eye is now uncovered, and a third line is 
seen between the two, with which it should be per- 
fectly parallel. If there is a want of harmony on 
the part of the oblique muscles, this test will show 
it at once in a want of parallelism of the middle 
with the two other lines, the right end of the 



250 HETEROPHORIA. 

middle line pointing towards the bottom, and the 
left end towards the top, or vice versa, depending 
npon the nature of the individual case. The eye 
before which there is no prism is the one being 
tested; as, for instance, with a prism before the 
right eye, the patient's attention is directed to the 
middle line, which he sees with the left, If it is 
nearer the bottom, it shows left hyperphoria; if 
nearer the top, left cataphoria; if to the right, exo- 
phoria; to the left, esophoria. If the right ends 
of the middle and bottom lines converge, while the 
left ends diverge, the superior oblique of the left 
eye is shown to be below the normal strength. 
A, Figure 153, represents such a condition; B 
shows a weak- 
ness of the in- 
ferior oblique of 
the left eye. C 
shows a devia- 
tion of parallel- 
ism, being due 
to underaction 
1^.153. of the superior 
oblique of the right eye. D shows a weakness of 
the inferior oblique of the right eye." 

TREATMENT. 

"In the treatment, either concave or convex cyl- 
inders can be used, and if the insufficiency is in the 
superior oblique, the axis of the r concave cylinder 
must be placed in the lower nasal quadrant. If in 
the inferior oblique, the axis must be placed in the 
lower temporal quadrant. If, for exercise, the con- 







HETEROPHORIA. 251 

vex cylinders are chosen, the axis must be placed in 
the lower temporal quadrant for insufficiency of the 
superior obliques, and in the lower nasal quadrant 
for insufficiency of the superior obliques. The 
exercise may be commenced with a 0.50 D. to 1.00 
D. cylinder, and increased each day from 0.50 D to 
3.00 D. The time should not exceed twelve or 
fifteen minutes daily. The rythmic exercise, as 
in other forms of heterophoria, can be used to 
advantage.' ' 



CHAPTER XII. 



STRABISMUS. 



Strabismus is the term given to that condition 
of the eyes in which there is a deviation of the 
axes from parallelism or the normal, and in con- 
sequence of this deviation the two eyes do not fix 
an object simultaneously, although each may have 
a normal range of vision. As a rule, there is no 
diplopia (double vision), and the muscular error is 
functional, there being no paralysis. When paraly- 
sis exists, both eyes in certain meridians may fix an 
object at the same time, but in other directions one 
or the other eye will lag on account of paralysis of 
a certain muscle or muscles, and, as a rule, there is 
double vision in certain parts of the visual field. 
In paralysis or paresis of the extrinsic ocular mus- 
cles the deviation is not universal, only experienced 
in certain directions, and the habit of suppressing 
one image is less readily formed. Also, the devia- 
tion being variable, the image of the object is con- 
stantly flitting on and about the yellow spot, now 
exactly blending with the image of the fellow eye 
and again moving to one or another side; conse- 
quently more or less double vision is experienced. 

In what is ordinarily known as strabismus 
there is a deviation of the eyes from the normal, 
and hence but one eye fixes the object at a 

252 



STRABISMUS. 



253 



time, while the image of the object falls to one 
side of the yellow spot in the fellow eye and is 
ignored, thus preventing diplopia. If, however, the 
strabismus is very slight, the image will impinge 
upon the retina near the yellow spot and the 
patient not infrequently complains of diplopia. 

Strabismus may be permanent or temporary. 
Of the different kinds of strabismus, we have stra- 
bismus convergens (inward), strabismus diver gens 
(outward), strabismus sursumvergens (upward), and 
strabismus deorsumvergens (downward). If but one 
eye deviates, we call it monocular strabismus. In 
case of both axes deviating it is called binocular 
strabismus. If first one eye fixes the object and 
then the other, it is called alternating. Occasion- 
ally in convergent and divergent strabismus one 
eye will turn upward or downward as well as in- 
ward and outward; especially is this true in con- 
vergent strabis- 
mus. In the case 
of monocular stra- 
bismus the eye 
that does not fix 
the object is not 
equal in its vision 
to that of its fel- 
low, whereas in 
alternating strabismus the vision of each eye is 
equally good. The angle of deviation is frequently 
greater in one eye than in the other; that is to say, 
one eye has a wider range of excursion than the 
other. When the deviation of each eye is the 
same, it is called concomitant strabismus. 




254 STRABISMUS. 

To measure the strabismus several kinds of 
instruments have been devised, but no one of itself 
is perfectly satisfactory. Fig. 154 represents one of 
these instruments. The ordinary method of meas- 
urement is to have the patient fix an object at a 
distance (which he does with one eye), then mark 
the lower lids with pen and ink opposite the cen- 



Fig. 155. 

ter of the pupil of each eye; screen the eye 
fixed and cause the patient to look at the object 
with the other eye and while this eye is fixed 
mark the lids of both eyes opposite their pupils 
as before. Now, if the distances between the 
marks upon the lids of each eye be equal, the 



STRABISMUS. 255 

strabismus is concomitant and the amount can be 
estimated in mm. However, this is not an accurate 
method. The more nearly correct method is to 
take the measurement in degrees by means of the 
perimeter (Fig. 155). 

To obtain the angle of deviation in degrees, 
place the patient in front of the perimeter with 
the arc horizontal. Have the patient look at an 
object at a distance of several feet in a line with 
the zero of the arc, which is at the center; then 
by moving a lighted candle or lamp along the arc 
until the image of its name is seen in the center 
of the pupil of the deviating eye, the num- 
ber on the arc opposite the flame will indicate the 
degree of deviation. In case of a high degree of 
convergent strabismus when the squinting eye 
turns in under the nose so as not to admit of a 
reflex of the candle flame, a prism may be used 
that will cause the light to be thrown on to the 
center of the cornea, and half of the strength of 
the prism added to the amount given by the peri- 
meter will equal the degree of strabismus. Any 
deviation upward or downward can in a similar 
way be ascertained. In high degrees of myopia 
where the optic axis is at the inner side of the 
visual line there is an apparent convergent stra- 
bismus. 

CAUSES. 

The mother or attendant usually attributes the 
cause to a fall, fright, spasm, or some disease of 
childhood. She will tell you that Johnny's or 
Mary's eyes were perfectly straight until he or she 
had the measles, whooping-cough, mumps, diph- 



256 STRABISMUS. 

theria, etc., or until the eyes of the child were 
exposed to a strong light. You will almost always 
be informed, however, that the strabismus appeared 
about the fourth or fifth year of age, sometimes 
earlier and again later; usually about the time the 
child begins to use its power of accommodation; 
as when learning to read. 

Among the real causes of strabismus the most 
frequent are : hypermetropia, inyopia, amblyopia, 
muscular insufficiency, opacity of cornea, monocu- 
lar cataract, monocular amblyopia, atrophy of optic 
nerve, scotomata, etc. In convergent strabismus, 
hypermetropia is responsible for about eighty per 
cent ; while in divergent strabismus, myopia is 
associated with a large per cent. Occasionally, 
divergent strabismus results from an operation for 
convergent strabismus, too free dissection of the 
internal rectus having been made. Schweigger 
finds that among 325 cases of convergent strabis- 
mus 85 were emmetropic, 44 were myopic, and 196 
hyperopic; and in 100 cases of divergent strabis- 
mus 37 were emmetropic, 59 myopic, and 4 were 
hyperopic. Horner finds that in 236 cases of con- 
vergent strabismus 4 were emmetropic, 11 myopic, 
13 were antimetropic (one eye myopic, the other 
hyperopic), and 208 hyperopic. In 133 cases of 
divergent strabismus, 3 were emmetropic, 62 myopic, 
30 antimetropic, and 38 hyperopic. In hyperme- 
tropia, as we have seen, the power of accommoda- 
tion is brought constant!}' into use, whether the 
eye is regarding near or distant objects, and the 
higher the degree of hypermetropia the greater is 
the demand upon the accommodative power of the 



STRABISMUS. 257 

eye. It Has been shown by Donders that the 
effect of accommodation is facilitated by conver- 
gence of the eyes. So in the hyperopic eye the 
addnctors are brought much into use, until finally 
there is a preponderance of power developed in the 
internal recti over that of the external recti, and 
convergent squint is induced. In myopia, when 
the eye is adjusted for near objects or for diver- 
gent rays, there is no necessity for exercising the 
accommodative power and the adductor muscles; 
consequently, there is no convergence, and for want 
of stimulus the internal recti may become inert 
and the abductors gain preponderance of power, 
resulting in divergent strabismus. In case of 
monocular corneal opacity, cataract, or ambly- 
opia from other causes, the defective eye does not 
fix the object observed and is allowed to turn at 
will uncontrolled ; this may result in divergence or 
convergence. 

Astigmatism, anisometropia, and antimetropia 
are frequently associated with strabismus. In a 
slight amount of strabismus there is occasionally 
diplopia due to some form of heterophoria, but it 
is only when one image laps over or is near the 
other. This complication can frequently be cor- 
rected by simply decentering the glass required to 
correct the anomaly of refraction ; or if there be 
no anomaly of refraction, but simply a muscular 
asthenopia, simple prisms with their bases turned 
toward the muscles to be relieved may suffice. 
Where there is decided deviation the image 
impinges upon the retina of the deviating eye so 
far from the macula that no cognizance is taken 



258 STRABISMUS. 

of it; that is to say, the image is ignored or sup- 
pressed, and then, from disuse, this eye suffers, and 
its vision frequently becomes seriously impaired. 
If the axes converge, the diplopia will be homon- 
ymous ; if they diverge, it will be heteronymous. 

Time of Appearance of Strabismus. — Strabismus 
may be congenital, appearing at birth, but is usu- 
ally not noticed until the child begins to fix its 
vision upon small objects, as, for instance, when it 
begins to learn to read; or, in other words, when 
it first brings its power of accommodation into use. 
The muscles of accommodation and those of adduc- 
tion have their innervation from the same source, 
and when the former are brought into requisition 
there is an associated movement of the latter. 

Divergent strabismus appears, as a rule, much 
later in life than convergent, especially if it is 
dependent upon myopia, as myopia does not exist 
at birth and is usually several years in reaching 
its highest degree of development. It is very 
seldom that strabismus sursumvergens or deorsum- 
vergens exists unassociated with convergent or 
divergent strabismus. 

TREATMENT. 

In slight degrees of strabismus at its incipiency, 
if there be ametropia or muscular asthenopia, the 
glasses required for the ametropia or the astheno- 
pia will occasionally correct the strabismus. Eser- 
ine may be used to relieve the ciliary muscle, and 
hence, the accommodative power; or atropine to 
wholly suspend its action. In prescribing glasses 
for strabismus depending on myopia or hyperme- 



STRABISMUS. 259 

tropia, the weaker muscles can also be relieved by 
decentering the glasses required to correct the error 
of refraction; as, for instance, in hyperopia the con- 
vex glass decentered outward has the effect of a 
prism with base outward, thus relieving the exter- 
nal rectus. In myopia the concave glass should 
also be decentered outward, that the base of the 
prism be towards the nose, thus relieving the 
internal rectus. However, the effect of prisms has 
not thus far proven always satisfactory. 

In cases of strabismus of a considerable degree, 
and once permanently developed, no other treat- 
ment than surgical will suffice. Frequently the 
patient with strabismus, especially if convergent, 
will complain of a drawing sensation or a tension 
with pain in the eyes. This is due to the contin- 
ued strain of the internal recti muscles drawing 
the eyes inward, and no treatment will relieve this 
other than tenotomy of the internal recti muscles; 
and then, if there be any anomaly of refraction, it 
should be corrected by the required glasses. In 
high degrees of convergent strabismus, or in case 
of weak abductors, the external recti have to be 
advanced with or without tenotomy. 

When should tenotomy be made? As a rule, the 
operation should not be made under four years of 
age, neither should it be delayed beyond the sixth 
or eighth year; for, at first, the squint is alternat- 
ing and the vision is equally good in both eyes; 
but if the child is allowed to go on with the 
deviation, after a time it learns to look with but 
one eye, ignoring the image of the other so as to 
avoid double vision, and then, from disuse, the eye 



260 STRABISMUS. 

not fixing may become irreparably injnred. The 
object of tenotomy is then not only to improve 
the appearance of the child, bnt to preserve sight 
and prevent other complications which are liable 
to arise from the anomaly, if long neglected; such 
as impaired vision, severe pain in the eye, frontal 
and temporal headaches, St. Vitus's dance, and even 
insanity. It is, I repeat, very important that a 
timely operation and adjustment of glasses be 
made; but the operation must be carefully and 
judiciously made. The manner and extent of the 
operation should be governed by the amount of 
strabismus and the amount of error of refraction. 
There should never be too free a dissection of one mus- 
cle, but rather a partial tenotomy of the muscle in 
each eye. If there be but a slight deviation, 
say three or four mm., and it seems to be con- 
fined to one eye, an operation may be limited 
to this eye ; but in ninety per cent of all 
cases both eyes should be operated upon; that 
is to say, in case of convergent strabismus both 
internal recti are at fault and the operation should 
be divided between the two eyes. If there be but 
a slight amount of deviation, it may be advisable 
to make graduated tenotomy, severing only a part 
of the tendon fibres, say the central ones; if this 
does not suffice, the operation can be repeated. The 
extent of the excision should be governed by the 
amount of deviation to be corrected. If the opera- 
tion be confined to one eye and a free dissection 
of the muscle be made, an over-correction is liable 
to follow, and then the delicate operation of advance- 



STRABISMUS. 



261 



merit to correct 
this fault must be 
made. Trie young 
lady (Fig. 156) was 
operated upon for 
convergent stra- 
bismus when a 
child. The opera- 
tion was confined 
to one eye, a free 
division and dis- 
section of the in- 
ternal rectus was 
evidently made, 
and the result was 
that the eye turned 



,mk 



>,, 





Fur. 157. 



outward, with 
marked lagoph- 
thalmus. Disfig- 
urement from the 
operation, besides 
the loss of the eye 
from disuse, result- 
ed. In this case, to 
correct the fault I 
was obliged to ad- 
vance the internal 
rectus; as merely 
dividing the exter- 
nal would not cor- 
r e c t the diver- 
gence. I found 



262 STRABISMUS. 

the internal muscle so atrophied that there were 
merely a few shreds of tendon remaining, but I suc- 
ceeded in attaching them to the sclera by means of 
the conjunctiva near the margin of the cornea. 
The vision of the deviating eye previous to the 
operation, December 10, 1891, was too; ten days sub- 
sequent to the operation, when the second photo- 
graph was taken (Fig. 157), the vision of the eye 
was rW; showing a decided improvement by correct- 
ing the deviation so as to bring the eye into co- 
ordination with its fellow, thus allowing the images 
of objects looked at to fall upon its macula lutea. 
The cosmetic effect, as the photograph (Fig. 157) 
shows, is all that could be desired, as the divergence 
is accurately corrected and the lagophthalmus 
nearly so; which, to the young lady, being a singer, 
was of paramount consideration. 

In case of divergent strabismus with myopia 
it is, as a rule, advisable to advance the internal 
rectus as well as to tenotomize the external, for 
the internal muscle in these cases is usually insuffi- 
cient, and tenotomy alone of the external does not 
suffice. Also in a very pronounced case of conver- 
gent strabismus, especially if it is associated with 
a high degree of hypermetropia, it is frequently 
advisable to advance the external as well as to 
sever the internal rectus; in fact, in many cases a 
complete correction of the squint cannot be secured 
without resorting to advancement of the external. 

The question of dealing with strabismus in its 
different forms with the various phases and com- 
plications is of greater magnitude than is gener- 
ally thought ; and simply making tenotomy of cer- 



STRABISMUS. 263 

tain tendons is by no means the only considera- 
tion. It is often a grave question whether tenot- 
omy, espec.aiiy in children, should be made. Fre- 
quently the affection among these little patients 
can be corrected without resorting to surgical inter- 
ference; besides, if the operation is not properly 
and judiciously made, sequences may follow which 
prove even more disastrous than the previous con- 
dition. The general practitioner, unless he is pre- 
pared and is able to cope with all the different 
phases and complications that may arise, being 
competent of eliciting and detecting the different 
forms of heterophoria and the anomalies of refrac- 
tion, correcting the same, is not warranted in under- 
taking to operate upon these cases. While it is 
not difficult to sever the tendon, yet it is fre- 
quently most difficult to correct the strabismus and 
obtain perfect results. 

As has been said, convergent strabismus espe- 
cially must be corrected early ; for here the deviat- 
ing eye soon learns to suppress the image, and 
from want of stimulus or from disuse becomes 
irretrievably impaired in its vision. 

The steps for advancement are as folk>ws : 
Separate the lids with speculum; grasp the con- 
junctiva with rat-toothed forceps near the margin 
of cornea opposite the insertion of muscle; dissect 
down to the muscle, exposing the tendon ; then, 
with strabismus hook, hook up the tendon, render- 
ng it tense, clip off the external fibres at the 
nsertion, also clip away any redundancy of con- 
junctiva on either side; then, with curved needle 
threaded with silk, pass through conjunctiva at 



264 



STRABISMUS. 



superior portion at the margin of the cornea, then 
through tendon at its insertion, then pass through 
the conjunctiva above opposite the point of the 
insertion of the tendon. Pass a second curved 
needle threaded with silk through the conjunctiva, 
at the liinbus inferior portion, thence through the 
lower portion of the tendon, lastly through the 




big. 136. 

conjunctiva opposite the insertion of tendon. Then^ 
with curved scissors with convex surface next to 
the sclera, clip off the remaining portion of tendon 
as close to the insertion as possible, taking care 
not to sever the silk. The sutures should be in- 
serted into the conjunctiva at equal distance above 
and below the line of tendon or muscle, so that 



STRABISMUS. 



265 



when they are tied they advance the mnscle, which 
reattaches itself in its normal direction.* 

On advancing in pronounced cases it is usu- 
ally necessary to make tenotomy of the opposing 
muscle. Care must be exercised in this not to 
clip too freely, or over-correction and lagophthal- 
mus may result. 




Fig. 159. 

In the child, Susie H — 



-, of Shockley, Neb., 
aged four years (Fig. 158), the convergence was 
alternating, although somewhat confined to the left 
eye. The ophthalmoscope showed five and one- 
half dioptres of hyperopia, and the angle of devia- 
tion was over fifty-five degrees in each eye, accord- 
ing to the perimeter. In this case, I made com- 
plete tenotomy of both internal recti, with the 

♦Irately I do not always sever the muscle, but fold it upon itself. 



,66 



STRABISMUS. 



result, as the picture shows (Fig 1-59), of completely 
correcting the strabismus. The picture was taken 
one week subsequent to the operation, January 8, 
1892. In this case, immediately after the opera- 
tion, the left eye deviated outward, but with the 
glasses it soon came to the proper position. 

The picture of Miss Flora B (Plate X), 

aged 20, shows a convergent strabismus, which was 
alternating without any manifest hyperopia; the 
vision of either eye was 18. The convergent stra- 
bismus of the right eye was 5 mm., and of the 
left 7 mm. The left eye was 2 mm. higher than 
the right. Complete mydriasis revealed a slight 
amount of hyperopic astigmatism of either eye, 
but scarcely more than is found in the ordinary 
so-called emmetropic eye. In this ^ase it was 
necessary to make complete tenotomy of the inter- 
nal rectus of each eye, as both muscles were 
strongly developed; and to correct the sursumver- 
gens I also made tenotomy of the superior rectus 
of the left eye, thus restoring perfect balance of 
the several ocular muscles, as the picture (Plate 
XI) indicates. 

The glasses, with the -operation, have dispelled 
all asthenopic symptoms, and the worried, anxious 
expression with the facial lineaments has disap- 
peared, giving place to a complacent, amiable 
expression, which is really the true index of her 
disposition, as shown by the picture (Plate XI). 

An interesting feature of this case is that here 
we had a decided convergent strabismus with 
scarcely any ametropia, and no hereditary tendency. 



Plate X. 





*' 






3T^ 




. 


V 






"Tr*^ 


M ... • i 



Plate XI. 




STRABISMUS. 267 

The slight hyperopic astigmatism was corrected 
by a +0.25 D. C, axis 90°. 

Steps of the Operation of Tenotomy. — Having 
thoroughly cocainized the eyes with an eight per 
cent solution and rendered them aseptic by thor- 
oughly flushing the conjunctival sac with boric 
acid solution, we lay out the necessary instruments 
and are then ready for the operation. 

We place the patient upon the table, separate 
the lids with Noyes's speculum; with forceps, grasp 
the conjunctiva just below and within the inser- 
tion of the tendon, then, with blunt-pointed scis- 
sors, snip through the conjunctiva and subcon- 
junctiva, insert the scissors, and by a few clips 
free the insertion from surrounding tissue, then 
insert the strabismus hook back of the muscle 
insertion, draw the hook forward, taking care to 
gather all of the fibres of the tendon. Making 
tense the muscle, insert the blunt-pointed curved 
scissors, convex surface next to the sclera, between 
the eye and the hook, and sever the tendon as 
close to the sclera as possible. If the hook now 
passes freely up to the limbus, the entire tendon 
is severed. We pass through the same steps with 
the other eye. 

There is an advantage in the subconjunctival 
tenotomy over the dissecting from the limbus 
down to the tendon, as there is not the disfigure- 
ment of the eye by a sinking of the caruncula. 

The after-treatment consists simply in bandag- 
ing the eyes for a few days, thus preventing any 
accommodation or convergence, cleansing with anti- 
septic lotions, and the adjustment of required 
glasses on the removal of the bandage. If there 



268 



STRABISMUS 



be hyperopia or astigmatism, it is absolutely essen- 
tial that they be corrected by prompt and continu- 
ous use of proper glasses. 

The boy (Fig. 160) was operated on at the clinic 
and satisfactory results were obtained, but he failed 




Fig. 160. 

to come back. I saw him a few weeks after the oper- 
ation, when the eyes had again deviated inward, be- 
cause he had neglected to wear his glasses. This is 
an example of one of the failures, or partial failures, 
incident to neglect upon the part of the patient tcr 
wear the glasses prescribed for his ametropia. 



Plate XII. 




l. 2. 

Walter B , aged 12, came to the clinic December 8, 1893, wiih 

the following history: " Mother had six children, the youngest being 
seven years of age the oldest twenty-four. Nearly all have some defect- 
ive sight. This boy had successive attacks of brain trouble between 
the ages of two and a half and nine years. Lost sight of right eye 
entirely at six years, but recovered partially as health grew better. 
Had convulsions regularly from 5 p m. till midnight when the sight of 
the right eye was lost. The eyes were operated upon twice by an ocu- 
list, first in January, 1892, and again in February, 1892; but with little 
or no benefit" (Fig. 1). 

Vision of right eye = 20-160; with + 1.50 D., = 20-120. 

Vision of left eye = 20-40; with + 0.50 D., = 20-30. 

The ophthalmoscope did not show any pathological condition 3 of 
the retina of the amblyopic eye, though glasses would improve the 
vision of this eye but slightly. A mydriatic revealed hyperopia 3.50 D. 
of the left eye. The angle of deviation of the right eye was about fifty 
degrees. There was such a preponderance of power* of the adductors 
in this case, and weakness of the abductors, that it was necessary to 
make advancement of the external rectus of the right eye, as well as 
tenotomy of both interni. This operation was made December 16, 
1893. December 23, R -f 1.50s. D. either eye. 

The second photograph (2) was taken three weeks subsequent to 
the operation, illustrating, as it does, a perfect correction of the squint. 
The vision of the right eye January 26, 1894, was 20-100; that of the left 
20-30, showing a considerable improvement in the vision of the ambly- 
opic eye, brought about by the operation and use of glasses. 



CHAPTER XIII. 



SPECTACLES. 



Under the head of spectacles I wish ta call 
especial attention to the different forms of eye- 
glasses, and to the necessity of a perfect fit as to 
size, form, and style, as well as to the adjustment 
to the nose and face. In selecting glasses, it is of 
great necessity that they be secured to correct not 
only the errors of refraction, but also the anoma- 
lies of the extrinsic muscles. The oculist ferrets 
out the anomaly, prescribes the glasses with meas- 
urements as to size and style 
of frames, etc., and the optician 
should see that the mechanical 
part is perfectly done, and that 
the prescription is accurately 
filled; for if the glasses are not 
Flgl6L properly adjusted, they will not 

accomplish what is expected of them, and may even 
prove injurious. It is the optician's business, first, 
to see that the glass has its principal axis in its 
center (Fig. 161), for if the 
axis is eccentric, as shown in 
Fig. 162, bringing the center of 
such a glass opposite the pupil 
would not bring its optical cen- 
ter into the visual axis. The 
optician then should see that 





Fig. 162. 



270 



SPECTACLES. 



the glass is truly centered and that the center of 
each glass is opposite the pupil of the correspond- 
ing eye. (Figs. 163 and 164), 

If the frames are 
too large, too small, or 
are not properly 
poised, but are tilted, 
as in Figs. 165 and 166, or decentered, as in Figs. 

^ 167, 168, 169, the eye 
does not look through 




Fig. 163. 




Fig. 164. 



the center of the glass, 
but some other part. 
This produces the ef- 
fect of a prism, and 
inordinately taxes cer- 
tain muscles, provok- 
ing asthenopic symptoms. Care must be taken 

also that the glasses are properly poised on the 

nose, at the right height 

and distance from the eyes. 

If they are too high, the 

person looks through the' 

lower edge, or goes with 

head bowed; or if they are 

set too low, he must look 

through the upper edge, or go with head thrown 

back. If the glasses 
k are set too near, the 




Fig. 165. 




lashes are constantly 
striking them. A con- 
cave glass should be placed as near the eye as 
possible without interfering with the lashes; if not, 
the peripheral rays will not enter the pupil, and 





SPECTACLES. 271 

hence the retinal image will be smaller. The con- 
verse of this holds trne with a convex glass, for 
the further away the lens is (up to a certain limit), 
the more convergent the rays come to the eye and 

more will enter the pupil, 
and brighter and larger 
will be the image. If they 
are too far, the distance 
changes their focal power. 
Great care should be 
taken in selecting the saddle, or nose-piece. See that 
it not only fits the nose, but carries the glasses at the 
proper height and dis- 
tance from the eyes. 
If the saddle is too 

j . 1 Fig. 168. 

narrow and pinches 

the nose, it may provoke disease of the lachrymal 
apparatus. The size and style of the glass must 
be selected to suit the individual features. 

In taking the measurement of the spectacles, 

the pupillary dis- 
tance is the princi- 
pal consideration, 
Fig ' 169 " and next to that in 

importance is the selection of the saddle or nose- 
piece. People with a low or flat nose-bridge are 
not able to wear a pince nez. The glasses for dis- 
tant objects should set higher than those for near 
objects. Reading glasses should be in such a posi- 
tion as to permit seeing through the center with- 
out bowing the head, but merely lowering the eyes 
or directing the eye to an angle of 45° when the 
head is erect. 




272 



SPECTACLES. 



The temples of the spectacles should rest on 
the ears. If one ear is a little higher than the 
other, which is not uncommon, the bow should be 
correspondingly bent or tilted. No optician now- 
adays would think of giving to a child the same 
size frame and glass as to an adult; yet it is but 
a few years since any attention has been given to 
the special fitting of glasses to children. 

The nose-piece should have sufficient fiat sur- 
face so as not to cut the nose; a co'rk pad is light, 
aseptic, and prevents the saddle from cutting the 
nose. The width of the frames should be sufficient 
so as not to press too snugly the temples, and if 
the bows be hooked (Fig. 170), they must not hug 




Fig. 170. 

too closely the ears. Patients frequently complain 
of the bows cutting the ears, and so they put them 
through the hair ; this is liable to tilt the glasses. 
All these little details should be carefully 
looked after by the optician, for, as may be seen 
by the foregoing, the success of the glasses pre- 
scribed by the oculist depends much upon the opti- 
cian, the relation of the latter to the former being 
similar to that of the druggist to the physician. 



SPECTACLES. 



273 



Many patients object to wearing spectacles in 
the ordinary frames (Fig. 171), and prefer the nose- 
glass (Fig. 172). If the glasses are 
to be worn only for reading, sew- 
ing, or for near objects, the nose- 






fid 




Fig. 172. 

glass is allowable; bnt if they are 
for constant nse, the hook frames 
are best. The pinch-nose, for many 
people, especially for those of nerv- 
ous temperament, is a sonrce of 
annoyance, and produces or aggra- 
vates a neuralgic headache. If the 
pinch-nose is prescribed, it should 
fit properly and the spring should 
not be too strong. 

As before said, frequently patients 
come to us with frames which they 
perhaps have received as a present, 
or as heirlooms, wishing to have 
glasses set in them. These frames 
may be too wide or too narrow, 
and in no way fit the face, and, if 
used, would certainly do harm to 
the eyes. What mother would 
think of giving to the child grandmother's gloves 
or grandfather's boots, expecting the child to wear 
these heirlooms? Certainly this important little 
organ of vision, with its delicate mechanism, should 
be worthy of as much consideration as these other 



274 



SPECTACLES. 




members of the body. If cylindrical glasses are 
prescribed, they would better be placed in specta- 
cle frames, with hook bows, that the axis be secured 
in the desired meridian; especially if the glasses 
are for constant use. For myopes the hook frames 
are preferable. If the patient with astigmatism is 
desirous of using only the pinch-nose, the bar frame 
(Fig. 1 73) should be prescribed, as this more surely t 
secures the axis of 
the cylinder in the 
required meridian. 

For children, 
gold frames are the best, as steel will soon rust 
and break. 

PROTECTING GLASSES. 

As protecting glasses, the blue seem to be the 
best. It was thought at one time that the red 
rays were more irritating, hence green glasses, 
which exclude the red, were much in vogue; but 
it is not the red, but the orange rays which are 
irritating to the retina, and hence the blue glass, 
which excludes the orange rays, is the most pleas- 
ant to the eye. 

A large oval concavo-convex blue or smoked is 
the best; green should not be used. These pro- 
tecting glasses are liable to be poorly made, and 
of an inferior quality of glass; and so it is of 
importance that they be selected with care. They 
are of benefit in subduing the bright glare of the 
sunlight, especially at the seaside or in the tropics. 
They are also of benefit in protecting the eye 
from the glare of the white snow, and after the 



SPECTACLES. 



275 





use of a mydriatic. They are frequently useful in 
protecting trie eye after cataract extraction, in reti- 
nitis, and, in fact, in any condition where there is 
photophobia. The large glasses set in aluminum 
frames (Fig. 174), are of special use as protecting 

glasses for gripmen, 
firemen, brakemen, 
stone-cutters, etc. Gog- 
gles with wire gauze 
(Fig. 175) should be 
denounced and discarded, for if they are long worn 
they are sure to provoke inflammation of the con- 
junctiva. They retain the 
heat and effluvium of the 
body, and act as incubators 
for germs. They are very 
frequently responsible for Fig. 175. 

granulated lids, and for pannus with other compli- 
cations. Patients get in the habit of using gog- 
gles, and it is almost impossible to induce them to 
leave them off, but so long .as they persist in using 
them so long will their eyes continue to be sore. 

If their use were entirely 
abandoned, there would be 
as a result a large decrease 
of "sore eyes." The shade 
Fig. 176. (Fig. 176) is useful as a 

protector both from wind and dust as well as from 
bright light ; also when reading or sewing. 

BIFOCAL LENSES. 
A bifocal lens consists of two parts differing in 
their focus. In hyperopia or presbyopia, the upper 
is the weaker for distant, the lower being stronger 




276 



SPECTACLES. 



for near objects; in myopia, the upper should be 
the stronger, and the lower the weaker glass. 

The convex bifocal lenses have been used for a 
number of years as "split glasses'' (Fig. 177); but 
recently they are tendered less conspicuous, and 
therefore less objectionable, by the cementing of a 
small thin segment to the lower part, thus increas- 
ing the focal power of this part of the glass (Fig. 
178). 





Fig. 1 



Fig. 178. 



An attempt has been made to grind a solid lens 
with the lower portion of a stronger focal power 
(Fig. 179), but as yet such lenses are imperfect in 
their construction and have not proven satisfactory. 





Fig. 179. Fig. 180. 

What is known as the "Perfection" (Fig. 180) 
has given better satisfaction. This consists in 
cutting out the lower part of the glass for distant 
objects, and fitting the reading lens in its place. 
These glasses are convenient for hyperopic persons 
after they have become presbyopic; especially are 
they appreciated by public speakers and readers, 



aPECTACi^Eb. 277 

who have occasion to change their vision constantly 
from distant to near objects and vice versa. 

It has been suggested that these glasses be 
also used by aphakic people, thus enabling them 
to see distant and near objects with the same 
spectacles; but, from the chromatic aberration of 
these strong glasses, they are not satisfactory. 

For the public speaker who is simply presby- 
opic, the half eye-glass is convenient, especially if 
he needs to refer to his notes or manuscript. 

It is of importance that the oculist as well as 
the optician be able to ascertain the strength of 
glasses, as frequently it is the case that glasses 
put up in large quantities are accidentally thrown 
into the wrong box and the strength falsely 
marked. So it is not always safe to trust the 
number indicated on the glass by the shipper. 

To ascertain the strength of the glass, find its 
focal distance by holding the glass in front of a 
candle flame or a window and see where the image 
is distinctly formed on a white background, as a 
piece of paper. Or, find the glass that will exactly 
neutralize the one being tested; as for instance, if 
measuring a convex glass, place a concave glass in 
proximity to the other which will exactly neutral- 
ize the convex. The concave glass can be tested 
in a similar way. If you can see through the two 
as clearly as you see with the naked eye, you may 
know that the two glasses are neutralized. 

In conducting the examination, if you move the 
glasses in front of the eye when looking at a dis- 



278 SPECTACLES. 

tant object, as the test card, if the letters remain 
stationary, you may know that one glass neutral- 
izes the other; but if the glasses do not neutralize 
each, other, the letters will shift as the glasses are 
moved before the eyes one way or the other. If 
the plus glass is the stronger, they will move in 
the opposite direction; if the concave is the 
stronger, they will move in the same direction 
that the glasses are moved in front of the eyes. 

The Lens Measure, as described in the Appen- 
dix, is also useful in ascertaining the strength and 
axis of glasses. 

The dioptric (dia, through; and optomai] I see) 
is a substitute for the term meter, and is now used 
by oculists instead of the inch measure, thus gain- 
ing uniform measurement throughout the world, 
as the inch is not uniform. 

A dioptre corresponds to 39.37 inches. For 
practical purposes, we call it 40 ; that is to say, a 
glass of one dioptre has the effect of bringing 
parallel rays to a focus at a point 40 inches from 
the glass. 

The old way of enumerating the glasses was 
by the inch or a fraction thereof, as, for instance, 
a glass that would bring parallel rays to a focus 
at 40 inches was called tV; one at 20 inches was 
called A; one at 10 was called rV; etc. The new 
notation is by meter or dioptres. The following 
table shows the old enumeration in inches and 
their equivalents approximately in dioptres: 

Inches. Dioptres. Inches. Dioptres. 

160 0.25 60 0.67 

80 0.50 50 0.75 



SPECTACLES. 279 

Inches. Dioptres. Inches. Dioptres. 

40 1.00 7 5.50 

36 1.11 6i 6.00 

30 1.25 6 6.50 

24 1.50 51 7.50 

22 • 1.75 5 8.00 

20 2.00 4i 9.00 

18 2.25 4 ..• 10.00 

16 2.50 31 10.50" 

14 2.75 3* 11.00 

13 3.00 3i 12.00 

12..... 3.25 3 13.00 

11 3.50 21 14.00 

10 4.00 2h 16.00 

9 4.50 2.1 18.00 

8.,, 5.00 2 20.00 



APPENDIX. 



PART I. 



SYNOPSIS OF DATA GATHERED FROM THE EXAMI- 
NATION OF TWO THOUSAND AND FORTY SCHOOL- 
CHILDREN OF THE PUBLIC SCHOOLS OF KANSAS CITY, 
UNIVERSITIES OF KANSAS AND MISSOURI, STATE 
NORMAL AND OTHER DISTRICT SCHOOLS.* 

Of 2040 pupils examined, there were: 
1422 Americans. 67 Irish. 

129 Germans. 47 English. 

26 French. 11 Swedish. 

15 Scotch. 93 mixed. 

Of the 1422 Americans, 300, or 21.1 per cent, 
had some anomaly of refraction. 

Of the 129 Germans, 32, or 24.8 per cent, were 
ametropic. 

Of the 26 French, 5, or 19,2 per cent. 

" " 15 Scotch, 3, or 20 

" " 67 Irish, 20, or 29.87 

11 " 47 English, 8, or 17 

" " 11 Swedish, 3, or 27.2 

" ". 93 mixed, 22, or 23.6 

The Irish, Swedish, and Germans had the high- 
est per cent of ametropia; the English, French, 
Scotch, and American the lowest. Out of the 
whole number examined (2040), 1162 were girls and 
878 were boys. 458 had some ametropia. Of the 

-Extract from a paper read before the Ninth International Medioal Congreso 
at Washington, D. C, 1887. 

280 



APPENDIX. 281 

1162 girls, 290, or 24.9 per cent, were .ametropic. 
Of the 878 boys, 168, or 19.1 per cent, were ame- 
tropic, there being a larger per cent of anomalies 
among the girls than the boys. In three grades 
of one school, the color of the eyes was not taken, 
bnt of those taken there were: 

629i pairs of blue, 99 hazel, 

364 gray, 91 black. 

443£ brown, 
Of the 629* blue, 122, or 19.3 per cent, were 
ametropic. 

Of the 364 gray, 801, or 22.1 per cent. 
" " UM brown, 86i,. or 19.5 " 
" " 99 hazel, 32, or 32.3 " 
" " 91 black, 18, or 19.7 " 
Blue, brown, and black had the lowest per cent 
of affections, the hazel having to a marked degree 
the largest per cent of affections. Calling the blue 
and the gray the light-colored eyes, and the black, 
brown, and hazel the dark, the light have 20.3 per 
cent of affections and the dark 21.3 per cent of af- 
fections. In this calculation the eyes of the negroes 
were not considered. Out of the 2040 pupils — 
13, or 0.6 per cent, had strabismus, 
94, or 4.6 per cent, were myopic, 
202, or 9.9 per cent, were hyperopic, 
42, or 2.06 per cent, were astigmatic, 
99, or 4.8 per cent, had spasm of accommo- 
dation, and 
63, or 3.1 per cent, had latent hypermetropia. 
We find that hypermetropia predominated; if 
we add latent hypermetropia and spasm of accom- 
modation, saying nothing of astigmatism — of which 



282 



APPENDIX. 



the majority were hyperopic — we have 364 hyper- 
metropes to 94 myopes, or nearly four times as 
many hypermetropes as myopes, or over twice as 
many as all other anomalies taken together. All 
the grades from the primary through the gram- 
mar school, high school, normal school, and uni- 
versity were represented, but in no instance, except 
the Kansas State University, was there anything 
like a gradual increase of myopia or an}- of the 
anomalies, simply or collectively. In nearly all of 
the schools there seems to be a higher per cent of 
anomalies in the first years, then a little later in 
the course a marked diminution, and then again 
an increase. Probably many of those having some 
trouble, after remaining in school a short time, 
drop out, which would account for the diminution, 
and then spasm of accommodation and latent 
hypermetropia becoming manifest later on, or per- 
haps developing into myopia, would account for 
the increase in myopia. 

School-life, however, so far as I can gather by 
these examinations, has comparatively little to do 
in the development of these anomalies. That they 
exist, however, in a much greater degree than is 
generally supposed is very evident, and that con- 
tinuous use of the eyes (having these errors of 
refraction), whether in the school-room or out of 
it, if not corrected, is sure to have its evil conse- 
quences. The importance of a recognition of the 
existence of these anomalies, of their extreme fre- 
quency, and of detecting and correcting them, is 
obvious enough. We should take into considera- 
tion that spasm of accommodation and latent hyper- 



APPENDIX. 283 

metropia frequently exist, and that these affections 
often develop into myopia, and if recognized early 
and promptly treated by rest and glasses, much suf- 
fering and irremediable trouble is averted. Cohn 
and others may have been able, years ago, to trace 
the development of myopia to badly appointed 
school-rooms ; but here in America our school-rooms 
are so carefully arranged as to light, seats, desks, 
ventilation, etc., that we can scarcely attribute to 
the work in the school-room the cause of anomalies. 
In a very great degree these errors of refraction are 
congenital; frequently they are latent, and if the 
eyes were not over-taxed (for near work), the ame- 
tropia would never become manifest. The evil aris- 
ing from work in the school-room is that these errors 
of refraction are not perceived, and hence not cor- 
rected. If the teacher could be made to under- 
stand that the little pupil's complaining of head- 
ache, pain through the temples, and weakness of 
the eyes, or dimness of vision arose neither from 
stupidity nor desire to avoid study, but that these 
complaints were symptoms of some defect of the 
organ of vision; or, what would be better still, let 
a competent oculist carefully examine each child 
as he enters upon each year of study in the school- 
work, and his anomaly (if he has any) be corrected; 
errors of refraction would gradually diminish. 

CONCLUSIONS. 
1. I think that the principal information 
gained in these examinations is that 22.4 per cent 
of the school -children have some anomaly of refrac- 
tion or accommodation, which should be recognized 
and corrected early. 



284 APPENDIX. 

2. That the hazel eyes, of all the colors, seem 
to be the ones most affected. 

3. That the light eyes, upon the whole, are 
less liable to be ametropic than the dark. 

4. That the females have a larger per cent of 
anomalies than the males. 

5. That there is a much larger per cent of 
hypermetropia than of myopia. 

6. That spasm of accommodation is a frequent 
anomaly. 

Out of 458 of the full number of pupils 
having defective vision, the complete record of 
each eye of 408, taken separately, was kept, and 
of these, 326 had both eyes affected, although not 
equally so. Of the other 83 only one eye was 
affected. The relative vision of the right eye to 
the left, including all cases where but one only 
was affected as well as where both were, were 
found to be as 231:225; z. e., Vision of R. E.:V. 
of L. E.:: 231:225. 

From time to time, in the different medical 
journals, I have called attention to the great import- 
ance of having a careful examination made of school 
children's eyes by a competent oculist, that these 
different forms of ametropia may be recognized and 
timely treated, to prevent the serious consequences 
that are sure to follow in these ametrupes ignorant of 
the necessity of wearing glasses and of further care 
and protection. It should be urged upon the part 
of every school board to assist in making a law 
requiring examinations by competent oculists. 



In making- these examinations, I am especially indebted to Professor J. M. 
Greenwood, Superintendent of our city schools, and to Prof. J. T. Buchanan, Prin- 
cipal of the Kansas City High School, for their hearty co-operation in obtaining 
these statistics. 



APPENDIX. 



285 



PART II. 



Fig. 181 represents a cabinet for Holding various 
test types. It secures them from dust and warp* 
ing and guarantees their presence when required. 




Fig. 181. 



286 



APPENDIX. 



Figs. 183 and 184 represent a prism-measuring 
and lens-centering instrument. 

In order to ascertain the degree of a prism, trie 
latter is placed at the base of the instrument under 
the three prongs, and the indicator will point to 
the number at the upper part, indicating the 
strength of the prism in degrees. 

In determining 
the center of a 
lens the latter is 
placed upon the 
lower points o f 
the instrument, 
which are not, 
shown, as they are 
covered by the 
lens. The upper 
part of the instru- 
ment is then 
pressed down un- 
til the two outer 
points touch the 
lens, and when the 
indicator points to zero on the scale, the position 
of the central prong will indicate the center of 
the lens. 

The lens measure (Figs. 185, 186, 187) has two 
stationary points (C, C) and one movable (B), which 
rests upon a lever (D) with cogs at its extremity, 
which play in the cogs of a wheel at the center (G), 
to which a pointer is attached. The lever is acted 
upon by the spring (H), which projects the central 
post slightly beyond the outer ones. The steel 




Fig. 183. 



APPENDIX. 



287 



spring (I) acts up- 
on the indicator 
(K). 

When the three 
posts are applied 
firmly to a per- 
fectly plane sur- 
face, as a prism, 
the indicator will 
point to zero on 
the dial. If ap- 
plied to a convex 
lens, it will go be- 
yond the zero, and 
if the lens be 1 D., 




Vig. 185. 



288 



APPENDIX. 




Fig. 186 



the indicator will point to +1. If applied to a 
concave lens, it will be moved towards the zero 
aud will point to the number 
on the dial according to the de- 
gree of concavity. 

In case of plano-convex or 
concave only one side need be 
measured; namely, that of the 
convexity or concavity; but if 
it is bi -convex or bi-concave, 
both sides must be measured, 
and the sum of the two indicates the strength of 
the glass. 

If it is a cylinder, the glass must be rotated 
when applied to the posts until the pointer comes 
to zero. The straight line running through the 
three posts is the axis of the cylinder. To ascer- 
tain the strength of the cylinder rotate the glass 
or the instrument at 
right angles to the 
former position, or un- 
til the highest number 
possible is reached. If 
it is concave, the 
pointer will be on the 
minus side; if convex, 
on the plus side of zero. 
In concavo-convex 
(with the convexity Fi g .i87. 

preponderating), find the amount of the convex 
side; e. g., 5 D.; then find the amount of the con- 
cave side, and if that be, for instance, — 3 D., then 
subtract the 3 from the 5, and we have a +2 D. 




APPENDIX. 



289 



In coiivexoconcave lenses (with the concavity 
preponderating), subtract the amount of the con- 
vex side from that of the concave side, and the 
remainder gives the strength of the glass, which 
will be a minus. 




Fig. 188. 



F. A. Hardy & Co.'s instrument. 
tion see page 191. 



For descrip- 



290 APPENDIX. 



Test Types. 



No. I ■ Diamond. 

If men would enjoy the blessings of Republican Government, they must govern themselves by reason, by mutual counsel and 
consultation, by iense and feeling of general interest, and by the acquiescence of the minority in the will of the majority, properly ex- 
pressed; and above all, the military must be kept, according to the language of our Bill of Rights, in strict subordination to the civil 
authority. The long processions of children and youths which we see to-day issuing by thousands from our free schools prove the care 



No. 2. Pearl. 

and anxiety with which a protective government provides for the education and morals of the people. Every- 
where there is order, everywhere there is security, everywhere the law reaches to the highest and reaches 
to the lowest, to protect all their rights and to restrain all from wrong— and over all hovers Liberty. The 
English Colonists in America, generally speaking, were men who were seeking new homes in a new 



No. 3, Nonpareil. 

world. They brought with them their families and all that was most dear to them. 
They introduced the civilization of Europe into a wilderness without bringing with 
it the political institutions of Europe. The arts, science, and literature came with 
the settlers. The law of inheritance and descent came also, except that part of it which 



No. 4. Minion. 

recognizes the rights of primogeniture. The monarchy did not come, nor the 
aristocracy, nor the church as an estate of the realm. Political institutions 
were to be framed anew. A general social equality prevailed among the set- 
tlers, and an equality of political rights seemed the natural if not the neces- 



No. 5. Brevier. 

sary consequences. They brought with them a full portion of all the 
riches of the past, in science, in art, in morals, religion, and literature. 
The Bible came with them, and it is not to be doubted that to the free and 
universal reading of the Bible in that age men were much indebted for 

No. 6. L/Ong Primer. 

right views of civil liberty. The Bible teaches man his own indi- 
vidual responsibility, and his own dignity, and his equality with his 
fellow-men. Bacon, Locke, Shakespeare, and Milton came w r ith 
the colonists. Good English literature was read, spoken and 



APPENDIX. 291 



No. 7. Small Pica. 



written before the axe had made way to let in the sun upon 
the habitations and fields of Plymouth and Massachusetts; 
and, whatever may be said to the contrary, a correct use of th« 
English language is at this day more general throughout the 



No. 8. Pica. 



United States than it is throughout England herself. 
Another grand characteristic of the English colonies 
is that their political affairs were left to be managed 



No. 9. 2-line Brevier. 



by themselves. Home government, or 
the power of making in the colony the 
municipal laws which were to govern it, 



No. I O. 2-line I,ong- Primer. 



equality of rights. Her obliga- 
tions to Europe for science, art, 
laws, literature, and manners 



lO. II. 2-line Pica. 



America acknowledges 
as she ought with respect 
and gratification. Ameri- 



292 APPENDIX. 

No. 12. 3-line Pica. 

ca has furnished 
to Europe proof 
of the fact, that 



No. 13. 4-line Pica. 



popular in- 
stitutions, 
founded on 



No. I 4. 5-line Pica. 



equality 
and the 



D-.LX 






^--_- — i 

i ! ! 
i 

t — i — • 



D-.Iv 




t--i^ 





D-.XL, 






J-.XXX 







D-.XX 






D-.CLX 












1 1 


1 






! J 




• 
* i 

! j | 













D-.CXX 




D-.LXXX 






Index. 



a 

Page. 

Abductor Muscles 224 

Abductors, Strength of 228 

Aberration, Chromatic 51, 52 

Spherical 49 

Accommodation cf the 

Eye 59, 71-83 

Amplitude of 81 

Canal of Schlemm 73 

Catoptric Test 75-77 

Ciliary Body 72 

Ciliary Ligament 73 

Ciliary Processes 72-74 

Circular Fibres 72 

Dynamic Refraction 81 

Emmetropic Eye (Iwanoff).78 
Experiments of Hensen and 

Voelckers 82 

Fontana's Spaces 73 

Hyperopic Eye (Iwanoff ) . .78 
Ligamentum Pectinatum 

Iridis 79 

Mechanism of 81-83 

Meridional Fibres 73 

Myopic Eye (Iwanoff) 79 

Power of. .71 

Punctum Proximum 80 

Punctum Remotum 80 

Radiating Fibres 72 

Spasm of 169 

Static Refraction 81 

Territory or Range of 80 

Venous Canal 73 

Zone of Zinn 72 

Achromatic Lens 52 

Adductor Muscles 224 

Strength of 228 

Advancement Operation 263 

Alternating Strabismus 253 

Ametropia 65 

Ametropic Eye 65 

Amplitude of Accommodation. .81 



Page. 

Angle, Alpha 66 

Gamma 67 

Of Deviation 34 

Of Deviation in Strabismus 

255 

Of Incidence 22, 23, 34 

Of Reflection 22 

Of Refraction 34 

Optic 62 

Sine of 34 

Visual 61 

Anisometropia. . . .70, 205, 210-212 

Cause of 210 

Treatment of 211 

Anterior Chamber 54, 57 

Anterior Focal Line. 180 

Antimetropia 257 

Aperture of Lens 49 

Aphakia 69, 212-214 

Catoptric Test for 213 

Example of 212 

Symptoms of 213 

Treatment of 214 

Aphakic Eye 213 

Apparent Convergent Strabis- 
mus 255 

Apparent Strabismus 67 

Appearance of the Fundus. . . .113 

Appendix 280-289 

Cabinet for Test Types 285 

Conclusions .283, 284 

Latent Hypermetropia 282 

Lens-Centering Instru- 
ment 287 

Lens Measure. . . .286, 287, 288 
Prism-Measuring Instru- 
ment 286 

Prism Pile 285 

School-Life ....282 

Spasm of Accommodation. 2S2 

Synopsis of Data. 280, 2S1, 2S2 

Aqueous Humor 53, 57 



300 



INDEX. 



Page. 

Arteria Centralis Retinae 106 

Asthenopia 231 

Astigmatism 67, 177-209 

Anterior Focal Line 180 

Appearance of Disc in. . . .183 
Appearance of Fundus in. 183 
Astigmometer (Ophthal- 

mometre) 186 

Causes of 181 

Common to All Ryes 69 

Compound. 181 

Compound Hvperopic.69, 201 

Compound Myopic 69, 201 

Corneal 69, 178 

Cylindrical Glasses for 206 

Diagnosis of 184 

Discovery of 177 

Focal Interval 180 

Glasses for 203 

Hyperbolical Glasses 209 

Hypothetical Cases of. 200-203 

Irregular 69, 181 

Lenticular 69, 178 

Meridians of 68, 179 

Mixed 69, 181 

Mixed, with Hyperopia 

Predominating 201 

Mixed, with Myopia Pre- 
dominating 202 



Line. 



182, 



181 
199 
184 
181 
197 



Posterior Focal 

Prognosis of 

Pulsation of Veins in 

Regular 

Retinoscopy for 

Simple 181 

Simple Hvperopic 69, 200 

Simple Myopic 68, 200 

Stenopaic Disc 198 

Symptoms of 182 

Test with Chromoscope. . .194 
Test with Keratoscope. . . .19b 
Test with Ophthalmo- 
scope 196 

Test with Prisoptometer. .191 
Test with Trial Glasses ... 198 

Torical Glasses 208 

Treatment of 200 

Atropine (see Mydriatic). 

Axis, Optic 60 

Principal 25, 39 

Secondary 40 

B 

Beam of Light 21 

Bi-Cylinder 203 

Bifocal Lenses 275, 276 

Cement 276 

Perfection 276 

Solid 276 



Bifocal Lenses — Continued. 

Split Glasses 276 

Binocular Strabismus 253 

Blind Spot 58 

Brachvmetropia 132 

Bull's Optometer 124 

Burning Glass 46 

c 

Cabinet for Test Types 285 

Camera Obscura 47 

Canal of Petit 73 

Canal of Schlemm 73 

Capsule of Lens 54 

Cataphoria 152, 220 

Catoptric Test 75, 76, 213 

Center of Curvature 25 

Center of Rotation of Eyeball. .67 

Chambers of the Eye 54 

Anterior 54 

Posterior 54 

Vitreous 54 

Chorea 83 

Choroid 53 

Choroidal Ring 113 

Choroiditis 166 

Chromatic Aberration 51, 52 

Chromatic Glass 126, 195 

Chromatic Test 124, 163 

Chromoscope as a Test in 

Astigmatism 194 

Ciliary Ligament . . . = 73 

Ciliary Muscle 55 

Ciliary Neuralgia 83, 158 

Ciliary Processes 53, 74 

Ciliary Region 78 

Circular Fibres of Ciliary 

Muscle 72 

Coccius 82 

Color 51 

Compound Astigmatism 181 

Concave Lens 37, 42 

Concave Mirrors 25-28 

Concavo-Convex Lens 37 

Concomitant Strabismus 253 

Conicity of the Cornea 209 

Conjugate Foci 26, 40 

Consanguinity as a Cause of 

Myopia 147 

Convergent Rays 42 

Convergent Strabismus 253 

Convex Lens 37, 38 

Convex Mirrors.' 25, 28, 31 

Convexo-Concave Lens 37 

Cornea 53 

Corneal Astigmatism 178 

Crossed Diplopia 231 

Crossed Cylinder 208 

Crystalline Lens 54 



INDEX. 



301 



Page. 

Cuignet's Test 162 

Curved Mirrors 23-32 

Concave. . . .. 25-28 

Convex 25, 28,31,32 

Cyclitis 166 

Cylinders 38 

Crossed 208 

Piano-Concave 207 

Piano-Convex 207 

Sphero-Concave 207 

Sphero-Convex 2v,7 

Cylindrical Glasses. . .206, 207, 274 

D 

Decomposition of Light 50 

DeWecker, M 209 

Dioptre 278 

Table of, Compared with 

Inches 279 

Dioptric 27S 

Dioptric System 66 

Diplopia 225 

Crossed 231 

Heteronymous 231 

Homonymous 230 

Direct Method 101-109 

To Measure Amount of 

Ametropia with. . .105-109 

Divergent Ray . 27 

Divergent Strabismus 253 

Donders 13, 64 

Double-Concave Lens 37, 42 

Double-Convex Lens 37 

Double Prism 87 

Dynamic Refraction 159, 213 

E 

Emmetropia 64 

Emmetropic Eye. 64 

Endometritis as a Cause of 

Ciliary Neuralgia 161 

Enlargement of Ophthalmo- 
scopic Images 114 

Epilepsy 233 

Eso-Cataphoria 221 

Esophoria 152, 220 

Exo-Cataphor\a 221 

Exophoria 220 

Extrinsic Muscles of the Eye. .221 

Eye, The 53-63 

Accommodation of 59 

Ametropic 65 

Anterior Chamber of 54,57 

Aqueous Humor of 53, 57 

Blind Spot of 58 

Capsule 54 

Choroid 53, 54 



Page. 
Eye, The— Continued. 

Ciliary Muscle. 55 

Ciliary Processes 53, 54 

Cornea of 53, 54 

Crystalline Lens 54, 57 

Dioptric System 60 

Emmetropic 64 

Fovea Centralis 56 

Hyaloid Fossa 58 

Hyaloid Membrane 57 

Hyperopic 66 

Iris 53,55 

Jacob's Membrane 55 

Layers of Retina 56 

Macula Lutea, or Yellow 

Spot 56 

Myopic 65 

Nodal Point of 60,62 

Optic Angle 62 

Optic Axis t50 

Optic Nerve 58 

Ora Serrata 55 

Posterior Chamber of. . .54, 57 

Retina 53,55 

Sclerotic 53,54 

Suspensory Ligament 58 

Visual Angle 61 

Visual Line 60 

Vitreous Body 57 

Vitreous Chamber 54, 57 



F 



172 



Facultative Accommodation . 

Far Point 80 

Far-Sightedness 156 

Field of Vision ]29 

Fin.te Rays 27 

Fixation Point 62 

Focal Interval 180 

Focal Length 38, 39 

Foci, Conjugate 26 

Focus, Principal. 27, 38 

Principal Virtual 28, 42 

Of Heat 46 

Virtual 27 

Fontana, Spaces of 73 

Fournet's Refractometer. 124 

Fovea Centralis 56, 61 

Frontal Headache 229 

Function of Accommodation. . . .59 

Cause of 74, 75 

General Conclusions in 

Regard to 74,75 

Fundus, Blood Vessels in 113 

In Astigmatism 183 

In Emmetropia 103, 105 

In Hyperopia 103, 105 

In Myopia 103, 105 

In Negroes 107 



302 



INDEX. 



Q 

Page. 

Glasses (see Lenses). 

For Anisometropia 211 

For Aphakia 214 

For Astigmatism 200-209 

For Heterophoria 246,247 

For Hypermetropia. . .170-176 

For Myopia 148-153 

For Presbyopia 218, 219 

For Strabismus 258, 259 

Goggles 275 

Hensen 82 

Helmholtz 11 

Heterophoria 220-251 

Abductors 224 

Adductors 224 

Card or Double Letter Test 

for 242 

Cataphoria 220 

Diplopia 225 

Eso-Cataphoria 221 

Esophoria 220 

Exo-Cataphoria 221 

Exophoria 220 

Extrinsic Muscles of the 

Eye 220 

Heteronymous or Crossed 

Diplopia. 231 

Homonymous Diplopia. . . .230 

Horopter 225 

Hyper-Esophoria 221 

Hyper-Exophoria 221 

Hyperphoria 152, 220 

Insufficiency of Oblique 

Muscles 249, 250 

Maddox's Double Prism 

Test for 240 

Maddox's Rod Test for. . . .238 

Orthophoria 220 

Point of Fixation 225 

Rhythmic Exercise with 

Prisms (Savage) 248 

Stevens's Phorometer 243 

Symptoms of 230 

Tenotomy for 247 

To Test Strength of the 

Muscles 235 

Treatment of 246 

Vertical Line Test for 236 

Von Grsefe's Line and Dot 

Test for 241 

Heteronymous Diplopia 231 

Hjort 82 

Homonymous Diplopia 230 

Homonymous Images 128 

Horopter, The 225 



Page. 

How to Examine the Eye 84 

How to Examine the Hyperopic 

Eye 168 

How to Project the Picture of 

the Fundus ] 17 

Hyaloid Artery 57 

Hyaloid Fossa . 58 

Hyaloid Membrane 57 

Hyperbolical Glasses 209 

Hyper-Esophoria 221 

Hyper-Exophoria 221 

Hypermetropia 65, 155-176 

Case of . . .172 

Causes of 161 

Chromatic Test for 163 

Cuignet's Test for 162 

Definition of 155 

Diagnosis of 162 

Dynamic Refraction 159 

Latent 159 

Manifest 159 

Microphthalmus 158 

Migraine as a Symptom of. 159 

Prisoptometry for 162 

Prognosis of 168 

Scheiner's Test for 163 

Sequelse to 169 

Static Refraction 157 

Symptoms of 159-161 

Test with Ophthalmoscope . 163 

Test with Trial Glasses 164 

Treatment of 170 

Hyperopia (see Hyperme- 
tropia) 65,155 

Hyperopic Astigmatism 167 

Hyperopic Eye Becoming Em- 
metropic 168 

Hyperphoria 152, 220 

Hysteria 83,235 



Ideal Eye 64 

Images, Formed by Concave 

Lenses 48 

Formed by Concave Mirrors . 29 
Formed by Convex Lenses. 42 
Formed by Convex Mirrors 31 

Inversion of 44 

Magnified 45 

Of the Hame in Catoptric 

Test 75,76 

Produced by Small Aper- 
tures 22 

Real ..24 

Shape of ..22 

Upright 31 

Virtual 24 

Index of Refraction .34 



INDEX. 



303 



Page. I 

Indirect Method 109 

Infinite Rays 27 

Insufficiency of Oblique Mus- 
cles 249,250 

Treatment of 250 

Insufficiency of Ocular Muscles 

(see Heterophoria) 220 

Iris 53 

Function of . ... 1 55 

Importance of in Accom- 
modation 75 

Iwanoff 78, 79, 157 

J 

Jacob's Membrane 56 

Javal 186 

Javal and Schicetz Ophthalmo- 

metre 186 

K 

Keratoconus 209 

Keratoscope 118 

As a test in Astigmatism. . . 193 
Koroscopy (see Shadow Test) . 

L 

Landolt 17,115 

Latent Hypermetropia 159, 282 

Lens-Centering Instrument 286 

Lens, Crystalline 57, 58 

Lenses 36-47 

Achromatic 52 

Aperture of 49 

Bi-Convex 38 

Bifocal 275,276 

Concavo-Convex 37 

Conjugate Foci of 40 

Convexo-Concave 37 

Cylindrical 38 

Decentration of 247 

Double-Concave 37, 42 

Double-Convex 37 

Focal Length of 38, 39 

Formation of Images by 

Concave 48 

Formation of Images by 

Convex 42 

Hyperbolical 209 

Optical Center of 39 

Piano-Concave 37 

Piano-Convex 37 

Principal Axis of 39 

Principal Focus 38 

Principal Virtual Focus of 

Concave 42 

Secondary Axis of 40 

Spherical., 38 

Torical 208 



Page 

Lens Measure 278, 286 

Lenticular Astigmatism 178 

Liebreich's Ophthalmoscope. . . .99 

Light 21 

Beam of . .21 

Decomposition of 50, 51 

Definition of 21 

Of School-Room 146 

Pencil of 21 

Propagation of 21 

Ray of 21 

Recomposition of 50, 51 

Reflection of (see Reflection). 
Refraction of (see Refraction). 

Sources of 21 

Velocity of 35 

White 51 

Limbus "3 

Longitudinal Fibres of Ciliary 

Muscle 74 

Loring's Ophthalmoscope 9& 

M 

Macula Lutea 115 

Mania 83 

Manifest Hypermetropia 159 

Maddox 238 

Maddox's Double Prism Test. .240 

Maddox's Prism 249 

Maddox's Rod Test 238 

Mechanism of Accommoda- 
tion. . 72, 75,81 

Megalopsia. 138 

Meridians of Eye 179 

Metamorphopsia 138 

Microphthalmus 158 

Micropsia 138 

Microscope 46, 47 

Compound 46 

Eye-Piece of 47 

Objective of 47 

Simple 46 

Migraine 83, 159 

Mirrors 23-32 

Concave 25 

Convex 25 

Curved 23-25 

Images Formed by Concave . 29 
Images Formed by Convex . . 31 

Plane 2a 

Principal Focus of 2T 

Principal Virtual Focus of . .28 
Reflection from Concave. . . .25 
Reflection from Convex. . . .28 

Reflection from Plane 23 

Surfaces of Waters as 24 

Vertex of 25 

Mixed Astigmatism 69, 181 

Monocular Strabismus 253 



304 



Page. 

Morton's Ophthalmoscope 101 

Mueller, Heinrich 74 

Muscae Volitantes 142 

Muscles, External Optic 235 

Insufficienc}^ of 227, 229 

Static Power, or Latent 

Reserve Force 227 

To Detect Insufficiency of. 235 

To Test Strength of 235 

Muscular Asthenopia 60, 158 

Mydriasis 165, 168 

Mydriatic 

152, 159, 164, 165, 168, 171, 199 

In Astigmatism 204 

In Heterophoria 233 

Myopia 65, 132-154 

Case of. 142 

Causes of 132-137 

Consanguinity as a Cause of. 133 

Definition of 132 

Diagnosis of . . 139 

Electric Light 147 

Heredity as a Cause of 133 

Light 146 

Luxation for 154 

Malignant 140 

Medium 140 

Muscae Volitantes 142 

Pathology of 138 

Posterior Staphyloma as a 

Sequel to 133 

Print 145 

Prognosis of 139 

Rochester Burner 147 

Sequelae to 141 

Simple 140 

Symptoms of 137, 138 

Tobacco as a Cause of 147 

Treatment by Glasses 148 

Treatment, Prophylactic. . .143 
Type 145 

N 

Near Point 80 

Near-Sightedness (Myopia). . . .132 

Negative Angle Alpha 67 

Negro's Retina > .107 

Nerve, Optic 58, 106, 113 

Nettleship 120 

Neuralgic Headache 273 

Nicol's Prism 187 

Nodal Point 61, 62 

Normal Eye 64 

Noyes, Dr 229 

Noyes's Speculum 267 

o 

Oblique Method 96 

Oblique Muscles 222 

Ophthalmidium 158 



index. 

Page. 
Ophthalmometer, J. & S. .185, 186 
Ophthalmometer,Hardy's,191, 289 

Ophthalmoscope 97, 98, 163 

As a Means of Detecting 

Astigmatism 193 

Direct Method 101-109 

Indirect Method 109 

Liebreich's 100 

Loring's 98,99 

Morton's 101 

Oblique Method 96 

Ophthalmoscopy 96 

Optical Center 39 

Optic Angle 62 

Optic Axis 60 

Optic Disc 106 

Optic Nerve 58, 106, 113 

Ora Serrata 55 

Orthophoria 220, 239, 242 



Parallel Rays 21 

Pencil of Light 21 

Perimeter 129, 255 

Optometry by. 130 

Phorometer, Stevens's 243 

Phorometer, Prince's 24b 

Phorometer, Test with 245, 246 

Physiological Cup 113 

Pince-Nez 205,271 

Pinch-Nose 205 

Plane Mirrors 23 

Piano-Concave Lens 37 

Piano-Convex Lens 37 

Point of Fixation 225 

Positive Angle Alpha 67 

Posterior Chamber 54, 57 

Posterior Focal Line 181 

Posterior Staphyloma 108 

Power of Accommodation. .71, 78 

Presbyopia 214, 219 

Symptoms of 216 

Treatment of 218 

Principal Axis (see Axis). 

Principal Focus 27, 38 

Principal Virtual Focus (see Focus). 
Prism-Measuring and Lens- 
Centering Instrument . 286, 287 

Prisms 36 

Effect of 36 

Prisoptometer 94 

As a Test in Astigmatism. 191 

Prisoptometry 94, 162 

Progressive Myopia 140 

Punctutn Proximum 80 

Puuctum Remotum 80 

Pupillary Distance 271 

Pupilometer 151 

Pi:piloscopy 1 18 



INDEX. 



305 



R 

Page. 
Radiating Fibres of Ciliary 

Muscle 72 

Rsehlmann, M 209 

Range of Accommodation 80 

Ranney, Dr 234 

Ray of Light 21 

Convergent 42 

Divergent 27 

Finite 27 

Infinite 27 

Parallel 21 

Real Image 24 

Recomposition of Light 50, 51 

Recti Muscles 222 

Reflection of Light 21-32 

Angle of Incidence 22 

Angle of Reflection 22 

Beam of Light . .21 

Center of Curvature 25 

Concave Mirror 25 

Conjugate Foci 26 

Convergent Rays 27 

Convex Mirror. 25 

Curved Mirror 23, 25 

Divergent Rays 27 

Finite Rays 27 

Focus 26 

Images Formed by Concave 

Mirrors 29-31 

Images Produced by Con- 
vex Mirrors 31 

Images Produced by Small 

Apertures 22 

Infinite Rays 27 

Laws of 22 

Light 21 

Mirrors 23 

Pencil of Light 21 

Plane Mirror 23 

Principal Axis 25 

Principal Focus of Concave 

Mirror 27 

Principal Virtual Focus. . . .28 

Ray of Light 21 

Real Image 24 

Reflection from Concave 

Mirrors 25 

Reflection from Convex 

Mirrors 28 

Reflection from Plane Mir- 
rors 23 

Secondary Axis 30 

Surfaces of Waters as Mir- 
rors 24 

Vertex of Mirror 25 

Virtual Focus 27 

Virtual Image 24 



Page. 
Refraction of Eye,Dynamic 159, 213 

Static 81 

Refraction of Light 33-52 

Achromatic Lens 52 

Angle of Deviation 34 

Angle of Incidence 34 

Angle of Refraction 34 

Burning-Glass 46 

Camera Obscura 47 

Cause of . . . . 35 

Chromatic Aberration 51 

Color of a Body 51 

Compound Microscope 46 

Conjugate Foci . 40 

Cylinders 38 

Decomposition of Light. . .50 

Effects of 35 

Formation of Images by 

Double-Concave Lenses 48 
Formation of Images by 
Double-Convex Lenses 

42-46 

Importance of Subject of. . .33 

Index of 34 

Lenses 36, 37 

Microscope 46, 47 

Optical Center of Lens 39 

Principal Virtual Focus of 

Lens 42 

Prisms 36 

Recomposition of Light. . . .50 

Secondary Axis 40 

Simple Microscope 46 

Spectrum, Solar 50 

Spherical Aberration. ..... .49 

Telescope 47 

Refractive Media 118 

Retina 53 

Retinoscopy. . . 118 

In Astigmatism 197 

Roosa, Dr 176 

Rotation, Center of 67 



Saddle of Spectacles 271, 272 

Savage, Dr 241, 247, 248 

Rhythmic Exercises with 

Prisms by 248 

Scheiner's Test 127, 163 

Schicetz .1S6 

School-Room, Ventilation, 

Seats, etc., of 153 

Schweigger 256 

Sclera 53 

Sclerotic 54 

Sclerotic Ring 113 

Secondary Axis 40 

Shade 275 

Shadow Test 118, 162 



306 



Index. 



Page. 

Sichel, Prof 217 

Simple Hvperopic Astigma- 
tism." 69,200 

Simple Myopic Astigma- 
tism 68,200 

Sine of Angle 34 

Skiascopy 118, 162, 197 

Smith, Dr. Priestley 154 

Snellen's Test Card 198 

Spasm of Accommoda- 

tion 135,169,282 

Spectacles 269-279 

Bifocal Lenses 275, 276 

Cement < Bifocals 276 

Cylindrical Glasses 274 

Dioptre .278 

Dioptric 278 

Goggles 275 

Gold Frames 274 

Hooked Bows 272 

Lens-Measure 278 

Neuralgic Headache Pro- 
duced by Pince-Nez. . 273 

Nose-Glass .273 

Ordinary Frames 273 

Perfection Bifocals 276 

Pince-Nez 271 

Principal Axis of Glass 269 

Protecting Glasses 274 

Pupillary Distance 271 

Saddle or Nose-Piece.27l, 272 

Shades 275 

Solid Bifocals 276 

Split Glasses 276 

Strength of Glass 277 

Table of Dioptres Com- 
pared with Inches. . . .279 

Temples of 272 

Spectrum 50 

Spencer, Dr 243 

Spherical Aberration 49 

Spherical Lenses 38 

Sphero-Cylinder 204 

Staphyloma 166 

Static'Refraction 81 

Stenopaic Disc 198 

Stevens, Dr 220, 234 

Phorometer of 243 

Strabismus 252 

Advancement Operation 

for.. 263-266 

Alternating 253 

Binocular 253 

Causes of 255 

Concomitant 253 

Convergens 253 

Definition of 252 

Deorsumvergens 253 



Page. 

Strabismus — Continued. 

Divergens 253 

Monocular 253 

Permanent 253 

Sursumvergens 253 

Temporary 253 

Tenotomy for 259-263, 267 

Time of Appearance of. . .258 
Treatment 258 

Suspensory Ligament 58 



Telescope 47 

Temples of Spectacles 272 

Temporal Headache 229 

Tenotomy, How Made 267 

When It Should be Made. .259 
Territory or Range of Accom- 
modation 80 

Test, Catoptric 75-77 

Chromatic 124,163 

Chromoscope 194 

Cuignet's 162 

For Astigmatism 90 

For Hyperopia 89 

For Myopia 88 

Keratoscope 93 

Maddox's Double Prism. . 240 

Maddox's Rod 238 

Ophthalmometre (Javal and 

Schioetz) 186 

Ophthalmoscope 96 

Phorometer 243 

Prisoptometer 94, 95 

Pupiloscopy 118 

Retinoscopy 118 

Schemer's 127, 163 

Shadow 118, 162 

Skiascopy 118, 162, 197 

Trial Box 85-93 

Von Grsefe's Line and Dot 241 
Test Types of Snellen and 

Giraud-Teulon 62 

Tic Douloureux 83 

Torical Glasses 208 

Trial Case 85,198 

Trial Frames 87 

Trial Glasses .85, 164 

Test with for Astigmatism 198 
Test with for Hyperopia. .164 

Test with for Myopia 139 

Tunics of the Eye . .' 53 

Type Best for School-Books ... 145 



u 



I Uveal Tract. 



INDEX. 



307 



V 

Page. 

Velocity of Ligh^ 35 

Venous Canal 73 

Vertex of Mirror 25 

Vertical Line Test in Hetero- 

phoria 236 

Virtual Focus 27 

Virtual Image 24 

Vision, Field of . . 129 

Visual Angle 61 

Smallest under Which an 

Object Can be Seen 62 

Visual Line 60, 225 

Vitreous Body 54 



Page. 

Vitreous Chamber 54, 57 

Vcelckers 82 

Von Grsefe 75 

Von Graefe's Line and Dot 

Test 241 

V 

Yeager's Test Type. 218 

Yellow Spot of Sommering 56 

Young 177 



Zone of Zinn. 



,73 



Among the authors consulted in writing this book are : Fuchs, 
Landolt, Wells, Nettleship, Hartridge, Bonders, Noyes, Juler, Meyer, 
Abadie, Williams, De Schweinitz, Helmholtz, Lawson, Swanzy, Schweig- 
ger, Schmidt-Rimpler, Valk, Roosa, Stevens, Savage, etc., and medical 
journals. 

MEDICAL BOOKS. 

ANOMALIES OF REFRACTION AND OF THE MUS- 
CLES OF THE EYE. By Flavel B. Tiffany, M.D. The book is 
printed on good paper, profusely illustrated and bound in cloth. 
Price, $3.00. 

SOJOURN AMONG THE OCULISTS OF EUROPE. By 

Flavel D. Tiffany, M.D. The book is printed on enameled paper and 
is handsomely bound in booklet form with embossed cover. 125 pages. 
Price, |1.00. 

PHYSICIAN'S RECORD BOOK. By Flavel B. Tiffany, M.D. 
There are two different forms — one for the ophthalmologist, and 
another combined for the ophthalmologist, otologist, rhinologist, and 
laryngologist. Price of combined book, $5.00. Oculist's book only, of 
365 pages, $5.00. 



HUDSON-KIMBERLY PUBLISHING Co. 

Kansas City, Mo. 



NOV 12 1900 



